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+\input texinfo
+@setfilename gdbint.info
+@c $Id: gdbint.texinfo,v 1.1 1994/06/10 13:34:28 paul Exp $
+
+@ifinfo
+@format
+START-INFO-DIR-ENTRY
+* Gdb-Internals: (gdbint). The GNU debugger's internals.
+END-INFO-DIR-ENTRY
+@end format
+@end ifinfo
+
+@ifinfo
+This file documents the internals of the GNU debugger GDB.
+
+Copyright 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
+Contributed by Cygnus Support. Written by John Gilmore.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+@ignore
+Permission is granted to process this file through Tex and print the
+results, provided the printed document carries copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+
+@end ignore
+Permission is granted to copy or distribute modified versions of this
+manual under the terms of the GPL (for which purpose this text may be
+regarded as a program in the language TeX).
+@end ifinfo
+
+@setchapternewpage off
+@settitle GDB Internals
+@titlepage
+@title{Working in GDB}
+@subtitle{A guide to the internals of the GNU debugger}
+@author John Gilmore
+@author Cygnus Support
+@page
+@tex
+\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
+\xdef\manvers{\$Revision: 1.1 $} % For use in headers, footers too
+{\parskip=0pt
+\hfill Cygnus Support\par
+\hfill \manvers\par
+\hfill \TeX{}info \texinfoversion\par
+}
+@end tex
+
+@vskip 0pt plus 1filll
+Copyright @copyright{} 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+@end titlepage
+
+@node Top
+@c Perhaps this should be the title of the document (but only for info,
+@c not for TeX). Existing GNU manuals seem inconsistent on this point.
+@top Scope of this Document
+
+This document documents the internals of the GNU debugger, GDB. It is
+intended to document aspects of GDB which apply across many different
+parts of GDB (for example, @pxref{Coding Style}), or which are global
+aspects of design (for example, what are the major modules and which
+files document them in detail?). Information which pertains to specific
+data structures, functions, variables, etc., should be put in comments
+in the source code, not here. It is more likely to get noticed and kept
+up to date there. Some of the information in this document should
+probably be moved into comments.
+
+@menu
+* README:: The README File
+* Getting Started:: Getting started working on GDB
+* Debugging GDB:: Debugging GDB with itself
+* New Architectures:: Defining a New Host or Target Architecture
+* Config:: Adding a New Configuration
+* Host:: Adding a New Host
+* Native:: Adding a New Native Configuration
+* Target:: Adding a New Target
+* Languages:: Defining New Source Languages
+* Releases:: Configuring GDB for Release
+* Partial Symbol Tables:: How GDB reads symbols quickly at startup
+* Types:: How GDB keeps track of types
+* BFD support for GDB:: How BFD and GDB interface
+* Symbol Reading:: Defining New Symbol Readers
+* Cleanups:: Cleanups
+* Wrapping:: Wrapping Output Lines
+* Frames:: Keeping track of function calls
+* Remote Stubs:: Code that runs in targets and talks to GDB
+* Longjmp Support:: Stepping through longjmp's in the target
+* Coding Style:: Strunk and White for GDB maintainers
+* Clean Design:: Frank Lloyd Wright for GDB maintainers
+* Submitting Patches:: How to get your changes into GDB releases
+* Host Conditionals:: What features exist in the host
+* Target Conditionals:: What features exist in the target
+* Native Conditionals:: Conditionals for when host and target are same
+* Obsolete Conditionals:: Conditionals that don't exist any more
+* XCOFF:: The Object file format used on IBM's RS/6000
+@end menu
+
+@node README
+@chapter The @file{README} File
+
+Check the @file{README} file, it often has useful information that does not
+appear anywhere else in the directory.
+
+@node Getting Started
+@chapter Getting Started Working on GDB
+
+GDB is a large and complicated program, and if you first starting to
+work on it, it can be hard to know where to start. Fortunately, if you
+know how to go about it, there are ways to figure out what is going on:
+
+@itemize @bullet
+@item
+This manual, the GDB Internals manual, has information which applies
+generally to many parts of GDB.
+
+@item
+Information about particular functions or data structures are located in
+comments with those functions or data structures. If you run across a
+function or a global variable which does not have a comment correctly
+explaining what is does, this can be thought of as a bug in GDB; feel
+free to submit a bug report, with a suggested comment if you can figure
+out what the comment should say (@pxref{Submitting Patches}). If you
+find a comment which is actually wrong, be especially sure to report that.
+
+Comments explaining the function of macros defined in host, target, or
+native dependent files can be in several places. Sometimes they are
+repeated every place the macro is defined. Sometimes they are where the
+macro is used. Sometimes there is a header file which supplies a
+default definition of the macro, and the comment is there. This manual
+also has a list of macros (@pxref{Host Conditionals}, @pxref{Target
+Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
+Conditionals}) with some documentation.
+
+@item
+Start with the header files. Once you some idea of how GDB's internal
+symbol tables are stored (see @file{symtab.h}, @file{gdbtypes.h}), you
+will find it much easier to understand the code which uses and creates
+those symbol tables.
+
+@item
+You may wish to process the information you are getting somehow, to
+enhance your understanding of it. Summarize it, translate it to another
+language, add some (perhaps trivial or non-useful) feature to GDB, use
+the code to predict what a test case would do and write the test case
+and verify your prediction, etc. If you are reading code and your eyes
+are starting to glaze over, this is a sign you need to use a more active
+approach.
+
+@item
+Once you have a part of GDB to start with, you can find more
+specifically the part you are looking for by stepping through each
+function with the @code{next} command. Do not use @code{step} or you
+will quickly get distracted; when the function you are stepping through
+calls another function try only to get a big-picture understanding
+(perhaps using the comment at the beginning of the function being
+called) of what it does. This way you can identify which of the
+functions being called by the function you are stepping through is the
+one which you are interested in. You may need to examine the data
+structures generated at each stage, with reference to the comments in
+the header files explaining what the data structures are supposed to
+look like.
+
+Of course, this same technique can be used if you are just reading the
+code, rather than actually stepping through it. The same general
+principle applies---when the code you are looking at calls something
+else, just try to understand generally what the code being called does,
+rather than worrying about all its details.
+
+@item
+A good place to start when tracking down some particular area is with a
+command which invokes that feature. Suppose you want to know how
+single-stepping works. As a GDB user, you know that the @code{step}
+command invokes single-stepping. The command is invoked via command
+tables (see @file{command.h}); by convention the function which actually
+performs the command is formed by taking the name of the command and
+adding @samp{_command}, or in the case of an @code{info} subcommand,
+@samp{_info}. For example, the @code{step} command invokes the
+@code{step_command} function and the @code{info display} command invokes
+@code{display_info}. When this convention is not followed, you might
+have to use @code{grep} or @kbd{M-x tags-search} in emacs, or run GDB on
+itself and set a breakpoint in @code{execute_command}.
+
+@item
+If all of the above fail, it may be appropriate to ask for information
+on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
+wondering if anyone could give me some tips about understanding
+GDB''---if we had some magic secret we would put it in this manual.
+Suggestions for improving the manual are always welcome, of course.
+@end itemize
+
+Good luck!
+
+@node Debugging GDB
+@chapter Debugging GDB with itself
+If gdb is limping on your machine, this is the preferred way to get it
+fully functional. Be warned that in some ancient Unix systems, like
+Ultrix 4.2, a program can't be running in one process while it is being
+debugged in another. Rather than typing the command @code{@w{./gdb
+./gdb}}, which works on Suns and such, you can copy @file{gdb} to
+@file{gdb2} and then type @code{@w{./gdb ./gdb2}}.
+
+When you run gdb in the gdb source directory, it will read a
+@file{.gdbinit} file that sets up some simple things to make debugging
+gdb easier. The @code{info} command, when executed without a subcommand
+in a gdb being debugged by gdb, will pop you back up to the top level
+gdb. See @file{.gdbinit} for details.
+
+If you use emacs, you will probably want to do a @code{make TAGS} after
+you configure your distribution; this will put the machine dependent
+routines for your local machine where they will be accessed first by
+@kbd{M-.}
+
+Also, make sure that you've either compiled gdb with your local cc, or
+have run @code{fixincludes} if you are compiling with gcc.
+
+@node New Architectures
+@chapter Defining a New Host or Target Architecture
+
+When building support for a new host and/or target, much of the work you
+need to do is handled by specifying configuration files;
+@pxref{Config,,Adding a New Configuration}. Further work can be
+divided into ``host-dependent'' (@pxref{Host,,Adding a New Host}) and
+``target-dependent'' (@pxref{Target,,Adding a New Target}). The
+following discussion is meant to explain the difference between hosts
+and targets.
+
+@heading What is considered ``host-dependent'' versus ``target-dependent''?
+
+@dfn{Host} refers to attributes of the system where GDB runs.
+@dfn{Target} refers to the system where the program being debugged
+executes. In most cases they are the same machine, in which case
+a third type of @dfn{Native} attributes come into play.
+
+Defines and include files needed to build on the host are host support.
+Examples are tty support, system defined types, host byte order, host
+float format.
+
+Defines and information needed to handle the target format are target
+dependent. Examples are the stack frame format, instruction set,
+breakpoint instruction, registers, and how to set up and tear down the stack
+to call a function.
+
+Information that is only needed when the host and target are the same,
+is native dependent. One example is Unix child process support; if the
+host and target are not the same, doing a fork to start the target
+process is a bad idea. The various macros needed for finding the
+registers in the @code{upage}, running @code{ptrace}, and such are all in the
+native-dependent files.
+
+Another example of native-dependent code is support for features
+that are really part of the target environment, but which require
+@code{#include} files that are only available on the host system.
+Core file handling and @code{setjmp} handling are two common cases.
+
+When you want to make GDB work ``native'' on a particular
+machine, you have to include all three kinds of information.
+
+The dependent information in GDB is organized into files by naming
+conventions.
+
+Host-Dependent Files
+@table @file
+@item config/*/*.mh
+Sets Makefile parameters
+@item config/*/xm-*.h
+Global #include's and #define's and definitions
+@item *-xdep.c
+Global variables and functions
+@end table
+
+Native-Dependent Files
+@table @file
+@item config/*/*.mh
+Sets Makefile parameters (for @emph{both} host and native)
+@item config/*/nm-*.h
+#include's and #define's and definitions. This file
+is only included by the small number of modules that need it,
+so beware of doing feature-test #define's from its macros.
+@item *-nat.c
+global variables and functions
+@end table
+
+Target-Dependent Files
+@table @file
+@item config/*/*.mt
+Sets Makefile parameters
+@item config/*/tm-*.h
+Global #include's and #define's and definitions
+@item *-tdep.c
+Global variables and functions
+@end table
+
+At this writing, most supported hosts have had their host and native
+dependencies sorted out properly. There are a few stragglers, which
+can be recognized by the absence of NATDEPFILES lines in their
+@file{config/*/*.mh}.
+
+@node Config
+@chapter Adding a New Configuration
+
+Most of the work in making GDB compile on a new machine is in specifying
+the configuration of the machine. This is done in a dizzying variety of
+header files and configuration scripts, which we hope to make more
+sensible soon. Let's say your new host is called an @var{xxx} (e.g.
+@samp{sun4}), and its full three-part configuration name is
+@code{@var{xarch}-@var{xvend}-@var{xos}} (e.g. @samp{sparc-sun-sunos4}). In
+particular:
+
+In the top level directory, edit @file{config.sub} and add @var{xarch},
+@var{xvend}, and @var{xos} to the lists of supported architectures,
+vendors, and operating systems near the bottom of the file. Also, add
+@var{xxx} as an alias that maps to
+@code{@var{xarch}-@var{xvend}-@var{xos}}. You can test your changes by
+running
+
+@example
+./config.sub @var{xxx}
+@end example
+@noindent
+and
+@example
+./config.sub @code{@var{xarch}-@var{xvend}-@var{xos}}
+@end example
+@noindent
+which should both respond with @code{@var{xarch}-@var{xvend}-@var{xos}}
+and no error messages.
+
+Now, go to the @file{bfd} directory and
+create a new file @file{bfd/hosts/h-@var{xxx}.h}. Examine the
+other @file{h-*.h} files as templates, and create one that brings in the
+right include files for your system, and defines any host-specific
+macros needed by BFD, the Binutils, GNU LD, or the Opcodes directories.
+(They all share the bfd @file{hosts} directory and the @file{configure.host}
+file.)
+
+Then edit @file{bfd/configure.host}. Add a line to recognize your
+@code{@var{xarch}-@var{xvend}-@var{xos}} configuration, and set
+@code{my_host} to @var{xxx} when you recognize it. This will cause your
+file @file{h-@var{xxx}.h} to be linked to @file{sysdep.h} at configuration
+time. When creating the line that recognizes your configuration,
+only match the fields that you really need to match; e.g. don't match
+match the architecture or manufacturer if the OS is sufficient
+to distinguish the configuration that your @file{h-@var{xxx}.h} file supports.
+Don't match the manufacturer name unless you really need to.
+This should make future ports easier.
+
+Also, if this host requires any changes to the Makefile, create a file
+@file{bfd/config/@var{xxx}.mh}, which includes the required lines.
+
+It's possible that the @file{libiberty} and @file{readline} directories
+won't need any changes for your configuration, but if they do, you can
+change the @file{configure.in} file there to recognize your system and
+map to an @file{mh-@var{xxx}} file. Then add @file{mh-@var{xxx}}
+to the @file{config/} subdirectory, to set any makefile variables you
+need. The only current options in there are things like @samp{-DSYSV}.
+(This @file{mh-@var{xxx}} naming convention differs from elsewhere
+in GDB, by historical accident. It should be cleaned up so that all
+such files are called @file{@var{xxx}.mh}.)
+
+Aha! Now to configure GDB itself! Edit
+@file{gdb/configure.in} to recognize your system and set @code{gdb_host}
+to @var{xxx}, and (unless your desired target is already available) also
+set @code{gdb_target} to something appropriate (for instance,
+@var{xxx}). To handle new hosts, modify the segment after the comment
+@samp{# per-host}; to handle new targets, modify after @samp{#
+per-target}.
+@c Would it be simpler to just use different per-host and per-target
+@c *scripts*, and call them from {configure} ?
+
+Finally, you'll need to specify and define GDB's host-, native-, and
+target-dependent @file{.h} and @file{.c} files used for your
+configuration; the next two chapters discuss those.
+
+
+@node Host
+@chapter Adding a New Host
+
+Once you have specified a new configuration for your host
+(@pxref{Config,,Adding a New Configuration}), there are three remaining
+pieces to making GDB work on a new machine. First, you have to make it
+host on the new machine (compile there, handle that machine's terminals
+properly, etc). If you will be cross-debugging to some other kind of
+system that's already supported, you are done.
+
+If you want to use GDB to debug programs that run on the new machine,
+you have to get it to understand the machine's object files, symbol
+files, and interfaces to processes; @pxref{Target,,Adding a New Target}
+and @pxref{Native,,Adding a New Native Configuration}
+
+Several files control GDB's configuration for host systems:
+
+@table @file
+@item gdb/config/@var{arch}/@var{xxx}.mh
+Specifies Makefile fragments needed when hosting on machine @var{xxx}.
+In particular, this lists the required machine-dependent object files,
+by defining @samp{XDEPFILES=@dots{}}. Also
+specifies the header file which describes host @var{xxx}, by defining
+@code{XM_FILE= xm-@var{xxx}.h}. You can also define @code{CC},
+@code{REGEX} and @code{REGEX1}, @code{SYSV_DEFINE}, @code{XM_CFLAGS},
+@code{XM_ADD_FILES}, @code{XM_CLIBS}, @code{XM_CDEPS},
+etc.; see @file{Makefile.in}.
+
+@item gdb/config/@var{arch}/xm-@var{xxx}.h
+(@file{xm.h} is a link to this file, created by configure).
+Contains C macro definitions describing the host system environment,
+such as byte order, host C compiler and library, ptrace support,
+and core file structure. Crib from existing @file{xm-*.h} files
+to create a new one.
+
+@item gdb/@var{xxx}-xdep.c
+Contains any miscellaneous C code required for this machine
+as a host. On many machines it doesn't exist at all. If it does
+exist, put @file{@var{xxx}-xdep.o} into the @code{XDEPFILES} line
+in @file{gdb/config/mh-@var{xxx}}.
+@end table
+
+@subheading Generic Host Support Files
+
+There are some ``generic'' versions of routines that can be used by
+various systems. These can be customized in various ways by macros
+defined in your @file{xm-@var{xxx}.h} file. If these routines work for
+the @var{xxx} host, you can just include the generic file's name (with
+@samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
+
+Otherwise, if your machine needs custom support routines, you will need
+to write routines that perform the same functions as the generic file.
+Put them into @code{@var{xxx}-xdep.c}, and put @code{@var{xxx}-xdep.o}
+into @code{XDEPFILES}.
+
+@table @file
+@item ser-bsd.c
+This contains serial line support for Berkeley-derived Unix systems.
+
+@item ser-go32.c
+This contains serial line support for 32-bit programs running under DOS
+using the GO32 execution environment.
+
+@item ser-termios.c
+This contains serial line support for System V-derived Unix systems.
+@end table
+
+Now, you are now ready to try configuring GDB to compile using your system
+as its host. From the top level (above @file{bfd}, @file{gdb}, etc), do:
+
+@example
+./configure @var{xxx} +target=vxworks960
+@end example
+
+This will configure your system to cross-compile for VxWorks on
+the Intel 960, which is probably not what you really want, but it's
+a test case that works at this stage. (You haven't set up to be
+able to debug programs that run @emph{on} @var{xxx} yet.)
+
+If this succeeds, you can try building it all with:
+
+@example
+make
+@end example
+
+Repeat until the program configures, compiles, links, and runs.
+When run, it won't be able to do much (unless you have a VxWorks/960
+board on your network) but you will know that the host support is
+pretty well done.
+
+Good luck! Comments and suggestions about this section are particularly
+welcome; send them to @samp{bug-gdb@@prep.ai.mit.edu}.
+
+@node Native
+@chapter Adding a New Native Configuration
+
+If you are making GDB run native on the @var{xxx} machine, you have
+plenty more work to do. Several files control GDB's configuration for
+native support:
+
+@table @file
+@item gdb/config/@var{xarch}/@var{xxx}.mh
+Specifies Makefile fragments needed when hosting @emph{or native}
+on machine @var{xxx}.
+In particular, this lists the required native-dependent object files,
+by defining @samp{NATDEPFILES=@dots{}}. Also
+specifies the header file which describes native support on @var{xxx},
+by defining @samp{NAT_FILE= nm-@var{xxx}.h}.
+You can also define @samp{NAT_CFLAGS},
+@samp{NAT_ADD_FILES}, @samp{NAT_CLIBS}, @samp{NAT_CDEPS},
+etc.; see @file{Makefile.in}.
+
+@item gdb/config/@var{arch}/nm-@var{xxx}.h
+(@file{nm.h} is a link to this file, created by configure).
+Contains C macro definitions describing the native system environment,
+such as child process control and core file support.
+Crib from existing @file{nm-*.h} files to create a new one.
+
+@item gdb/@var{xxx}-nat.c
+Contains any miscellaneous C code required for this native support
+of this machine. On some machines it doesn't exist at all.
+@end table
+
+@subheading Generic Native Support Files
+
+There are some ``generic'' versions of routines that can be used by
+various systems. These can be customized in various ways by macros
+defined in your @file{nm-@var{xxx}.h} file. If these routines work for
+the @var{xxx} host, you can just include the generic file's name (with
+@samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
+
+Otherwise, if your machine needs custom support routines, you will need
+to write routines that perform the same functions as the generic file.
+Put them into @code{@var{xxx}-nat.c}, and put @code{@var{xxx}-nat.o}
+into @code{NATDEPFILES}.
+
+@table @file
+
+@item inftarg.c
+This contains the @emph{target_ops vector} that supports Unix child
+processes on systems which use ptrace and wait to control the child.
+
+@item procfs.c
+This contains the @emph{target_ops vector} that supports Unix child
+processes on systems which use /proc to control the child.
+
+@item fork-child.c
+This does the low-level grunge that uses Unix system calls
+to do a "fork and exec" to start up a child process.
+
+@item infptrace.c
+This is the low level interface to inferior processes for systems
+using the Unix @code{ptrace} call in a vanilla way.
+
+@item coredep.c::fetch_core_registers()
+Support for reading registers out of a core file. This routine calls
+@code{register_addr()}, see below.
+Now that BFD is used to read core files, virtually all machines should
+use @code{coredep.c}, and should just provide @code{fetch_core_registers} in
+@code{@var{xxx}-nat.c} (or @code{REGISTER_U_ADDR} in @code{nm-@var{xxx}.h}).
+
+@item coredep.c::register_addr()
+If your @code{nm-@var{xxx}.h} file defines the macro
+@code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
+set @code{addr} to the offset within the @samp{user}
+struct of GDB register number @code{regno}. @code{blockend} is the
+offset within the ``upage'' of @code{u.u_ar0}.
+If @code{REGISTER_U_ADDR} is defined,
+@file{coredep.c} will define the @code{register_addr()} function and use
+the macro in it. If you do not define @code{REGISTER_U_ADDR}, but you
+are using the standard @code{fetch_core_registers()}, you will need to
+define your own version of @code{register_addr()}, put it into your
+@code{@var{xxx}-nat.c} file, and be sure @code{@var{xxx}-nat.o} is in
+the @code{NATDEPFILES} list. If you have your own
+@code{fetch_core_registers()}, you may not need a separate
+@code{register_addr()}. Many custom @code{fetch_core_registers()}
+implementations simply locate the registers themselves.@refill
+@end table
+
+When making GDB run native on a new operating system,
+to make it possible to debug
+core files, you will need to either write specific code for parsing your
+OS's core files, or customize @file{bfd/trad-core.c}. First, use
+whatever @code{#include} files your machine uses to define the struct of
+registers that is accessible (possibly in the u-area) in a core file
+(rather than @file{machine/reg.h}), and an include file that defines whatever
+header exists on a core file (e.g. the u-area or a @samp{struct core}). Then
+modify @code{trad_unix_core_file_p()} to use these values to set up the
+section information for the data segment, stack segment, any other
+segments in the core file (perhaps shared library contents or control
+information), ``registers'' segment, and if there are two discontiguous
+sets of registers (e.g. integer and float), the ``reg2'' segment. This
+section information basically delimits areas in the core file in a
+standard way, which the section-reading routines in BFD know how to seek
+around in.
+
+Then back in GDB, you need a matching routine called
+@code{fetch_core_registers()}. If you can use the generic one, it's in
+@file{coredep.c}; if not, it's in your @file{@var{xxx}-nat.c} file.
+It will be passed a char pointer to the entire ``registers'' segment,
+its length, and a zero; or a char pointer to the entire ``regs2''
+segment, its length, and a 2. The routine should suck out the supplied
+register values and install them into GDB's ``registers'' array.
+(@xref{New Architectures,,Defining a New Host or Target Architecture},
+for more info about this.)
+
+If your system uses @file{/proc} to control processes, and uses ELF
+format core files, then you may be able to use the same routines
+for reading the registers out of processes and out of core files.
+
+@node Target
+@chapter Adding a New Target
+
+For a new target called @var{ttt}, first specify the configuration as
+described in @ref{Config,,Adding a New Configuration}. If your new
+target is the same as your new host, you've probably already done that.
+
+A variety of files specify attributes of the GDB target environment:
+
+@table @file
+@item gdb/config/@var{arch}/@var{ttt}.mt
+Contains a Makefile fragment specific to this target.
+Specifies what object files are needed for target @var{ttt}, by
+defining @samp{TDEPFILES=@dots{}}.
+Also specifies the header file which describes @var{ttt}, by defining
+@samp{TM_FILE= tm-@var{ttt}.h}. You can also define @samp{TM_CFLAGS},
+@samp{TM_CLIBS}, @samp{TM_CDEPS},
+and other Makefile variables here; see @file{Makefile.in}.
+
+@item gdb/config/@var{arch}/tm-@var{ttt}.h
+(@file{tm.h} is a link to this file, created by configure).
+Contains macro definitions about the target machine's
+registers, stack frame format and instructions.
+Crib from existing @file{tm-*.h} files when building a new one.
+
+@item gdb/@var{ttt}-tdep.c
+Contains any miscellaneous code required for this target machine.
+On some machines it doesn't exist at all. Sometimes the macros
+in @file{tm-@var{ttt}.h} become very complicated, so they are
+implemented as functions here instead, and the macro is simply
+defined to call the function.
+
+@item gdb/exec.c
+Defines functions for accessing files that are
+executable on the target system. These functions open and examine an
+exec file, extract data from one, write data to one, print information
+about one, etc. Now that executable files are handled with BFD, every
+target should be able to use the generic exec.c rather than its
+own custom code.
+
+@item gdb/@var{arch}-pinsn.c
+Prints (disassembles) the target machine's instructions.
+This file is usually shared with other target machines which use the
+same processor, which is why it is @file{@var{arch}-pinsn.c} rather
+than @file{@var{ttt}-pinsn.c}.
+
+@item gdb/@var{arch}-opcode.h
+Contains some large initialized
+data structures describing the target machine's instructions.
+This is a bit strange for a @file{.h} file, but it's OK since
+it is only included in one place. @file{@var{arch}-opcode.h} is shared
+between the debugger and the assembler, if the GNU assembler has been
+ported to the target machine.
+
+@item gdb/config/@var{arch}/tm-@var{arch}.h
+This often exists to describe the basic layout of the target machine's
+processor chip (registers, stack, etc).
+If used, it is included by @file{tm-@var{xxx}.h}. It can
+be shared among many targets that use the same processor.
+
+@item gdb/@var{arch}-tdep.c
+Similarly, there are often common subroutines that are shared by all
+target machines that use this particular architecture.
+@end table
+
+When adding support for a new target machine, there are various areas
+of support that might need change, or might be OK.
+
+If you are using an existing object file format (a.out or COFF),
+there is probably little to be done. See @file{bfd/doc/bfd.texinfo}
+for more information on writing new a.out or COFF versions.
+
+If you need to add a new object file format, you must first add it to
+BFD. This is beyond the scope of this document right now. Basically
+you must build a transfer vector (of type @code{bfd_target}), which will
+mean writing all the required routines, and add it to the list in
+@file{bfd/targets.c}.
+
+You must then arrange for the BFD code to provide access to the
+debugging symbols. Generally GDB will have to call swapping routines
+from BFD and a few other BFD internal routines to locate the debugging
+information. As much as possible, GDB should not depend on the BFD
+internal data structures.
+
+For some targets (e.g., COFF), there is a special transfer vector used
+to call swapping routines, since the external data structures on various
+platforms have different sizes and layouts. Specialized routines that
+will only ever be implemented by one object file format may be called
+directly. This interface should be described in a file
+@file{bfd/libxxx.h}, which is included by GDB.
+
+If you are adding a new operating system for an existing CPU chip, add a
+@file{tm-@var{xos}.h} file that describes the operating system
+facilities that are unusual (extra symbol table info; the breakpoint
+instruction needed; etc). Then write a
+@file{tm-@var{xarch}-@var{xos}.h} that just @code{#include}s
+@file{tm-@var{xarch}.h} and @file{tm-@var{xos}.h}. (Now that we have
+three-part configuration names, this will probably get revised to
+separate the @var{xos} configuration from the @var{xarch}
+configuration.)
+
+
+@node Languages
+@chapter Adding a Source Language to GDB
+
+To add other languages to GDB's expression parser, follow the following steps:
+
+@table @emph
+@item Create the expression parser.
+
+This should reside in a file @file{@var{lang}-exp.y}. Routines for building
+parsed expressions into a @samp{union exp_element} list are in @file{parse.c}.
+
+Since we can't depend upon everyone having Bison, and YACC produces
+parsers that define a bunch of global names, the following lines
+@emph{must} be included at the top of the YACC parser, to prevent
+the various parsers from defining the same global names:
+
+@example
+#define yyparse @var{lang}_parse
+#define yylex @var{lang}_lex
+#define yyerror @var{lang}_error
+#define yylval @var{lang}_lval
+#define yychar @var{lang}_char
+#define yydebug @var{lang}_debug
+#define yypact @var{lang}_pact
+#define yyr1 @var{lang}_r1
+#define yyr2 @var{lang}_r2
+#define yydef @var{lang}_def
+#define yychk @var{lang}_chk
+#define yypgo @var{lang}_pgo
+#define yyact @var{lang}_act
+#define yyexca @var{lang}_exca
+#define yyerrflag @var{lang}_errflag
+#define yynerrs @var{lang}_nerrs
+@end example
+
+At the bottom of your parser, define a @code{struct language_defn} and
+initialize it with the right values for your language. Define an
+@code{initialize_@var{lang}} routine and have it call
+@samp{add_language(@var{lang}_language_defn)} to tell the rest of GDB
+that your language exists. You'll need some other supporting variables
+and functions, which will be used via pointers from your
+@code{@var{lang}_language_defn}. See the declaration of @code{struct
+language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
+for more information.
+
+@item Add any evaluation routines, if necessary
+
+If you need new opcodes (that represent the operations of the language),
+add them to the enumerated type in @file{expression.h}. Add support
+code for these operations in @code{eval.c:evaluate_subexp()}. Add cases
+for new opcodes in two functions from @file{parse.c}:
+@code{prefixify_subexp()} and @code{length_of_subexp()}. These compute
+the number of @code{exp_element}s that a given operation takes up.
+
+@item Update some existing code
+
+Add an enumerated identifier for your language to the enumerated type
+@code{enum language} in @file{defs.h}.
+
+Update the routines in @file{language.c} so your language is included. These
+routines include type predicates and such, which (in some cases) are
+language dependent. If your language does not appear in the switch
+statement, an error is reported.
+
+Also included in @file{language.c} is the code that updates the variable
+@code{current_language}, and the routines that translate the
+@code{language_@var{lang}} enumerated identifier into a printable
+string.
+
+Update the function @code{_initialize_language} to include your language. This
+function picks the default language upon startup, so is dependent upon
+which languages that GDB is built for.
+
+Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
+code so that the language of each symtab (source file) is set properly.
+This is used to determine the language to use at each stack frame level.
+Currently, the language is set based upon the extension of the source
+file. If the language can be better inferred from the symbol
+information, please set the language of the symtab in the symbol-reading
+code.
+
+Add helper code to @code{expprint.c:print_subexp()} to handle any new
+expression opcodes you have added to @file{expression.h}. Also, add the
+printed representations of your operators to @code{op_print_tab}.
+
+@item Add a place of call
+
+Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
+@code{parse.c:parse_exp_1()}.
+
+@item Use macros to trim code
+
+The user has the option of building GDB for some or all of the
+languages. If the user decides to build GDB for the language
+@var{lang}, then every file dependent on @file{language.h} will have the
+macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
+leave out large routines that the user won't need if he or she is not
+using your language.
+
+Note that you do not need to do this in your YACC parser, since if GDB
+is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
+compiled form of your parser) is not linked into GDB at all.
+
+See the file @file{configure.in} for how GDB is configured for different
+languages.
+
+@item Edit @file{Makefile.in}
+
+Add dependencies in @file{Makefile.in}. Make sure you update the macro
+variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
+not get linked in, or, worse yet, it may not get @code{tar}red into the
+distribution!
+@end table
+
+
+@node Releases
+@chapter Configuring GDB for Release
+
+From the top level directory (containing @file{gdb}, @file{bfd},
+@file{libiberty}, and so on):
+@example
+make -f Makefile.in gdb.tar.Z
+@end example
+
+This will properly configure, clean, rebuild any files that are
+distributed pre-built (e.g. @file{c-exp.tab.c} or @file{refcard.ps}),
+and will then make a tarfile. (If the top level directory has already
+beenn configured, you can just do @code{make gdb.tar.Z} instead.)
+
+This procedure requires:
+@itemize @bullet
+@item symbolic links
+@item @code{makeinfo} (texinfo2 level)
+@item @TeX{}
+@item @code{dvips}
+@item @code{yacc} or @code{bison}
+@end itemize
+@noindent
+@dots{} and the usual slew of utilities (@code{sed}, @code{tar}, etc.).
+
+@subheading TEMPORARY RELEASE PROCEDURE FOR DOCUMENTATION
+
+@file{gdb.texinfo} is currently marked up using the texinfo-2 macros,
+which are not yet a default for anything (but we have to start using
+them sometime).
+
+For making paper, the only thing this implies is the right generation of
+@file{texinfo.tex} needs to be included in the distribution.
+
+For making info files, however, rather than duplicating the texinfo2
+distribution, generate @file{gdb-all.texinfo} locally, and include the files
+@file{gdb.info*} in the distribution. Note the plural; @code{makeinfo} will
+split the document into one overall file and five or so included files.
+
+
+@node Partial Symbol Tables
+@chapter Partial Symbol Tables
+
+GDB has three types of symbol tables.
+
+@itemize @bullet
+@item full symbol tables (symtabs). These contain the main
+information about symbols and addresses.
+@item partial symbol tables (psymtabs). These contain enough
+information to know when to read the corresponding
+part of the full symbol table.
+@item minimal symbol tables (msymtabs). These contain information
+gleaned from non-debugging symbols.
+@end itemize
+
+This section describes partial symbol tables.
+
+A psymtab is constructed by doing a very quick pass over an executable
+file's debugging information. Small amounts of information are
+extracted -- enough to identify which parts of the symbol table will
+need to be re-read and fully digested later, when the user needs the
+information. The speed of this pass causes GDB to start up very
+quickly. Later, as the detailed rereading occurs, it occurs in small
+pieces, at various times, and the delay therefrom is mostly invisible to
+the user. (@xref{Symbol Reading}.)
+
+The symbols that show up in a file's psymtab should be, roughly, those
+visible to the debugger's user when the program is not running code from
+that file. These include external symbols and types, static
+symbols and types, and enum values declared at file scope.
+
+The psymtab also contains the range of instruction addresses that the
+full symbol table would represent.
+
+The idea is that there are only two ways for the user (or much of
+the code in the debugger) to reference a symbol:
+
+@itemize @bullet
+
+@item by its address
+(e.g. execution stops at some address which is inside a function
+in this file). The address will be noticed to be in the
+range of this psymtab, and the full symtab will be read in.
+@code{find_pc_function}, @code{find_pc_line}, and other @code{find_pc_@dots{}}
+functions handle this.
+
+@item by its name
+(e.g. the user asks to print a variable, or set a breakpoint on a
+function). Global names and file-scope names will be found in the
+psymtab, which will cause the symtab to be pulled in. Local names will
+have to be qualified by a global name, or a file-scope name, in which
+case we will have already read in the symtab as we evaluated the
+qualifier. Or, a local symbol can be referenced when
+we are "in" a local scope, in which case the first case applies.
+@code{lookup_symbol} does most of the work here.
+
+@end itemize
+
+The only reason that psymtabs exist is to cause a symtab to be read in
+at the right moment. Any symbol that can be elided from a psymtab,
+while still causing that to happen, should not appear in it. Since
+psymtabs don't have the idea of scope, you can't put local symbols in
+them anyway. Psymtabs don't have the idea of the type of a symbol,
+either, so types need not appear, unless they will be referenced by
+name.
+
+It is a bug for GDB to behave one way when only a psymtab has been read,
+and another way if the corresponding symtab has been read in. Such
+bugs are typically caused by a psymtab that does not contain all the
+visible symbols, or which has the wrong instruction address ranges.
+
+The psymtab for a particular section of a symbol-file (objfile)
+could be thrown away after the symtab has been read in. The symtab
+should always be searched before the psymtab, so the psymtab will
+never be used (in a bug-free environment). Currently,
+psymtabs are allocated on an obstack, and all the psymbols themselves
+are allocated in a pair of large arrays on an obstack, so there is
+little to be gained by trying to free them unless you want to do a lot
+more work.
+
+@node Types
+@chapter Types
+
+Fundamental Types (e.g., FT_VOID, FT_BOOLEAN).
+
+These are the fundamental types that gdb uses internally. Fundamental
+types from the various debugging formats (stabs, ELF, etc) are mapped into
+one of these. They are basically a union of all fundamental types that
+gdb knows about for all the languages that gdb knows about.
+
+Type Codes (e.g., TYPE_CODE_PTR, TYPE_CODE_ARRAY).
+
+Each time gdb builds an internal type, it marks it with one of these
+types. The type may be a fundamental type, such as TYPE_CODE_INT, or
+a derived type, such as TYPE_CODE_PTR which is a pointer to another
+type. Typically, several FT_* types map to one TYPE_CODE_* type, and
+are distinguished by other members of the type struct, such as whether
+the type is signed or unsigned, and how many bits it uses.
+
+Builtin Types (e.g., builtin_type_void, builtin_type_char).
+
+These are instances of type structs that roughly correspond to fundamental
+types and are created as global types for gdb to use for various ugly
+historical reasons. We eventually want to eliminate these. Note for
+example that builtin_type_int initialized in gdbtypes.c is basically the
+same as a TYPE_CODE_INT type that is initialized in c-lang.c for an
+FT_INTEGER fundamental type. The difference is that the builtin_type is
+not associated with any particular objfile, and only one instance exists,
+while c-lang.c builds as many TYPE_CODE_INT types as needed, with each
+one associated with some particular objfile.
+
+@node BFD support for GDB
+@chapter Binary File Descriptor Library Support for GDB
+
+BFD provides support for GDB in several ways:
+
+@table @emph
+@item identifying executable and core files
+BFD will identify a variety of file types, including a.out, coff, and
+several variants thereof, as well as several kinds of core files.
+
+@item access to sections of files
+BFD parses the file headers to determine the names, virtual addresses,
+sizes, and file locations of all the various named sections in files
+(such as the text section or the data section). GDB simply calls
+BFD to read or write section X at byte offset Y for length Z.
+
+@item specialized core file support
+BFD provides routines to determine the failing command name stored
+in a core file, the signal with which the program failed, and whether
+a core file matches (i.e. could be a core dump of) a particular executable
+file.
+
+@item locating the symbol information
+GDB uses an internal interface of BFD to determine where to find the
+symbol information in an executable file or symbol-file. GDB itself
+handles the reading of symbols, since BFD does not ``understand'' debug
+symbols, but GDB uses BFD's cached information to find the symbols,
+string table, etc.
+@end table
+
+@c The interface for symbol reading is described in @ref{Symbol
+@c Reading,,Symbol Reading}.
+
+
+@node Symbol Reading
+@chapter Symbol Reading
+
+GDB reads symbols from "symbol files". The usual symbol file is the
+file containing the program which gdb is debugging. GDB can be directed
+to use a different file for symbols (with the ``symbol-file''
+command), and it can also read more symbols via the ``add-file'' and ``load''
+commands, or while reading symbols from shared libraries.
+
+Symbol files are initially opened by @file{symfile.c} using the BFD
+library. BFD identifies the type of the file by examining its header.
+@code{symfile_init} then uses this identification to locate a
+set of symbol-reading functions.
+
+Symbol reading modules identify themselves to GDB by calling
+@code{add_symtab_fns} during their module initialization. The argument
+to @code{add_symtab_fns} is a @code{struct sym_fns} which contains
+the name (or name prefix) of the symbol format, the length of the prefix,
+and pointers to four functions. These functions are called at various
+times to process symbol-files whose identification matches the specified
+prefix.
+
+The functions supplied by each module are:
+
+@table @code
+@item @var{xxx}_symfile_init(struct sym_fns *sf)
+
+Called from @code{symbol_file_add} when we are about to read a new
+symbol file. This function should clean up any internal state
+(possibly resulting from half-read previous files, for example)
+and prepare to read a new symbol file. Note that the symbol file
+which we are reading might be a new "main" symbol file, or might
+be a secondary symbol file whose symbols are being added to the
+existing symbol table.
+
+The argument to @code{@var{xxx}_symfile_init} is a newly allocated
+@code{struct sym_fns} whose @code{bfd} field contains the BFD
+for the new symbol file being read. Its @code{private} field
+has been zeroed, and can be modified as desired. Typically,
+a struct of private information will be @code{malloc}'d, and
+a pointer to it will be placed in the @code{private} field.
+
+There is no result from @code{@var{xxx}_symfile_init}, but it can call
+@code{error} if it detects an unavoidable problem.
+
+@item @var{xxx}_new_init()
+
+Called from @code{symbol_file_add} when discarding existing symbols.
+This function need only handle
+the symbol-reading module's internal state; the symbol table data
+structures visible to the rest of GDB will be discarded by
+@code{symbol_file_add}. It has no arguments and no result.
+It may be called after @code{@var{xxx}_symfile_init}, if a new symbol
+table is being read, or may be called alone if all symbols are
+simply being discarded.
+
+@item @var{xxx}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
+
+Called from @code{symbol_file_add} to actually read the symbols from a
+symbol-file into a set of psymtabs or symtabs.
+
+@code{sf} points to the struct sym_fns originally passed to
+@code{@var{xxx}_sym_init} for possible initialization. @code{addr} is the
+offset between the file's specified start address and its true address
+in memory. @code{mainline} is 1 if this is the main symbol table being
+read, and 0 if a secondary symbol file (e.g. shared library or
+dynamically loaded file) is being read.@refill
+@end table
+
+In addition, if a symbol-reading module creates psymtabs when
+@var{xxx}_symfile_read is called, these psymtabs will contain a pointer to
+a function @code{@var{xxx}_psymtab_to_symtab}, which can be called from
+any point in the GDB symbol-handling code.
+
+@table @code
+@item @var{xxx}_psymtab_to_symtab (struct partial_symtab *pst)
+
+Called from @code{psymtab_to_symtab} (or the PSYMTAB_TO_SYMTAB
+macro) if the psymtab has not already been read in and had its
+@code{pst->symtab} pointer set. The argument is the psymtab
+to be fleshed-out into a symtab. Upon return, pst->readin
+should have been set to 1, and pst->symtab should contain a
+pointer to the new corresponding symtab, or zero if there
+were no symbols in that part of the symbol file.
+@end table
+
+
+@node Cleanups
+@chapter Cleanups
+
+Cleanups are a structured way to deal with things that need to be done
+later. When your code does something (like @code{malloc} some memory, or open
+a file) that needs to be undone later (e.g. free the memory or close
+the file), it can make a cleanup. The cleanup will be done at some
+future point: when the command is finished, when an error occurs, or
+when your code decides it's time to do cleanups.
+
+You can also discard cleanups, that is, throw them away without doing
+what they say. This is only done if you ask that it be done.
+
+Syntax:
+
+@table @code
+@item struct cleanup *@var{old_chain};
+Declare a variable which will hold a cleanup chain handle.
+
+@item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
+Make a cleanup which will cause @var{function} to be called with @var{arg}
+(a @code{char *}) later. The result, @var{old_chain}, is a handle that can be
+passed to @code{do_cleanups} or @code{discard_cleanups} later. Unless you are
+going to call @code{do_cleanups} or @code{discard_cleanups} yourself,
+you can ignore the result from @code{make_cleanup}.
+
+
+@item do_cleanups (@var{old_chain});
+Perform all cleanups done since @code{make_cleanup} returned @var{old_chain}.
+E.g.:
+@example
+make_cleanup (a, 0);
+old = make_cleanup (b, 0);
+do_cleanups (old);
+@end example
+@noindent
+will call @code{b()} but will not call @code{a()}. The cleanup that calls @code{a()} will remain
+in the cleanup chain, and will be done later unless otherwise discarded.@refill
+
+@item discard_cleanups (@var{old_chain});
+Same as @code{do_cleanups} except that it just removes the cleanups from the
+chain and does not call the specified functions.
+
+@end table
+
+Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify that they
+``should not be called when cleanups are not in place''. This means
+that any actions you need to reverse in the case of an error or
+interruption must be on the cleanup chain before you call these functions,
+since they might never return to your code (they @samp{longjmp} instead).
+
+
+@node Wrapping
+@chapter Wrapping Output Lines
+
+Output that goes through @code{printf_filtered} or @code{fputs_filtered} or
+@code{fputs_demangled} needs only to have calls to @code{wrap_here} added
+in places that would be good breaking points. The utility routines
+will take care of actually wrapping if the line width is exceeded.
+
+The argument to @code{wrap_here} is an indentation string which is printed
+@emph{only} if the line breaks there. This argument is saved away and used
+later. It must remain valid until the next call to @code{wrap_here} or
+until a newline has been printed through the @code{*_filtered} functions.
+Don't pass in a local variable and then return!
+
+It is usually best to call @code{wrap_here()} after printing a comma or space.
+If you call it before printing a space, make sure that your indentation
+properly accounts for the leading space that will print if the line wraps
+there.
+
+Any function or set of functions that produce filtered output must finish
+by printing a newline, to flush the wrap buffer, before switching to
+unfiltered (``@code{printf}'') output. Symbol reading routines that print
+warnings are a good example.
+
+
+@node Frames
+@chapter Frames
+
+A frame is a construct that GDB uses to keep track of calling and called
+functions.
+
+@table @code
+@item FRAME_FP
+in the machine description has no meaning to the machine-independent
+part of GDB, except that it is used when setting up a new frame from
+scratch, as follows:
+
+@example
+ create_new_frame (read_register (FP_REGNUM), read_pc ()));
+@end example
+
+Other than that, all the meaning imparted to @code{FP_REGNUM} is imparted by
+the machine-dependent code. So, @code{FP_REGNUM} can have any value that
+is convenient for the code that creates new frames. (@code{create_new_frame}
+calls @code{INIT_EXTRA_FRAME_INFO} if it is defined; that is where you should
+use the @code{FP_REGNUM} value, if your frames are nonstandard.)
+
+@item FRAME_CHAIN
+Given a GDB frame, determine the address of the calling function's
+frame. This will be used to create a new GDB frame struct, and then
+@code{INIT_EXTRA_FRAME_INFO} and @code{INIT_FRAME_PC} will be called for
+the new frame.
+@end table
+
+@node Remote Stubs
+@chapter Remote Stubs
+
+GDB's file @file{remote.c} talks a serial protocol to code that runs
+in the target system. GDB provides several sample ``stubs'' that can
+be integrated into target programs or operating systems for this purpose;
+they are named @file{*-stub.c}.
+
+The GDB user's manual describes how to put such a stub into your target
+code. What follows is a discussion of integrating the SPARC stub
+into a complicated operating system (rather than a simple program),
+by Stu Grossman, the author of this stub.
+
+The trap handling code in the stub assumes the following upon entry to
+trap_low:
+
+@enumerate
+@item %l1 and %l2 contain pc and npc respectively at the time of the trap
+@item traps are disabled
+@item you are in the correct trap window
+@end enumerate
+
+As long as your trap handler can guarantee those conditions, then there is no
+reason why you shouldn't be able to `share' traps with the stub. The stub has
+no requirement that it be jumped to directly from the hardware trap vector.
+That is why it calls @code{exceptionHandler()}, which is provided by the external
+environment. For instance, this could setup the hardware traps to actually
+execute code which calls the stub first, and then transfers to its own trap
+handler.
+
+For the most point, there probably won't be much of an issue with `sharing'
+traps, as the traps we use are usually not used by the kernel, and often
+indicate unrecoverable error conditions. Anyway, this is all controlled by a
+table, and is trivial to modify.
+The most important trap for us is for @code{ta 1}. Without that, we
+can't single step or do breakpoints. Everything else is unnecessary
+for the proper operation of the debugger/stub.
+
+From reading the stub, it's probably not obvious how breakpoints work. They
+are simply done by deposit/examine operations from GDB.
+
+@node Longjmp Support
+@chapter Longjmp Support
+
+GDB has support for figuring out that the target is doing a
+@code{longjmp} and for stopping at the target of the jump, if we are
+stepping. This is done with a few specialized internal breakpoints,
+which are visible in the @code{maint info breakpoint} command.
+
+To make this work, you need to define a macro called
+@code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
+structure and extract the longjmp target address. Since @code{jmp_buf}
+is target specific, you will need to define it in the appropriate
+@file{tm-xxx.h} file. Look in @file{tm-sun4os4.h} and
+@file{sparc-tdep.c} for examples of how to do this.
+
+@node Coding Style
+@chapter Coding Style
+
+GDB is generally written using the GNU coding standards, as described in
+@file{standards.texi}, which is available for anonymous FTP from GNU
+archive sites. There are some additional considerations for GDB
+maintainers that reflect the unique environment and style of GDB
+maintenance. If you follow these guidelines, GDB will be more
+consistent and easier to maintain.
+
+GDB's policy on the use of prototypes is that prototypes are used
+to @emph{declare} functions but never to @emph{define} them. Simple
+macros are used in the declarations, so that a non-ANSI compiler can
+compile GDB without trouble. The simple macro calls are used like
+this:
+
+@example @code
+extern int
+memory_remove_breakpoint PARAMS ((CORE_ADDR, char *));
+@end example
+
+Note the double parentheses around the parameter types. This allows
+an arbitrary number of parameters to be described, without freaking
+out the C preprocessor. When the function has no parameters, it
+should be described like:
+
+@example @code
+void
+noprocess PARAMS ((void));
+@end example
+
+The @code{PARAMS} macro expands to its argument in ANSI C, or to a simple
+@code{()} in traditional C.
+
+All external functions should have a @code{PARAMS} declaration in a
+header file that callers include. All static functions should have such
+a declaration near the top of their source file.
+
+We don't have a gcc option that will properly check that these rules
+have been followed, but it's GDB policy, and we periodically check it
+using the tools available (plus manual labor), and clean up any remnants.
+
+@node Clean Design
+@chapter Clean Design
+
+In addition to getting the syntax right, there's the little question of
+semantics. Some things are done in certain ways in GDB because long
+experience has shown that the more obvious ways caused various kinds of
+trouble. In particular:
+
+@table @bullet
+@item
+You can't assume the byte order of anything that comes from a
+target (including @var{value}s, object files, and instructions). Such
+things must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in GDB,
+or one of the swap routines defined in @file{bfd.h}, such as @code{bfd_get_32}.
+
+@item
+You can't assume that you know what interface is being used to talk to
+the target system. All references to the target must go through the
+current @code{target_ops} vector.
+
+@item
+You can't assume that the host and target machines are the same machine
+(except in the ``native'' support modules).
+In particular, you can't assume that the target machine's header files
+will be available on the host machine. Target code must bring along its
+own header files -- written from scratch or explicitly donated by their
+owner, to avoid copyright problems.
+
+@item
+Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
+to write the code portably than to conditionalize it for various systems.
+
+@item
+New @code{#ifdef}'s which test for specific compilers or manufacturers
+or operating systems are unacceptable. All @code{#ifdef}'s should test
+for features. The information about which configurations contain which
+features should be segregated into the configuration files. Experience
+has proven far too often that a feature unique to one particular system
+often creeps into other systems; and that a conditional based on
+some predefined macro for your current system will become worthless
+over time, as new versions of your system come out that behave differently
+with regard to this feature.
+
+@item
+Adding code that handles specific architectures, operating systems, target
+interfaces, or hosts, is not acceptable in generic code. If a hook
+is needed at that point, invent a generic hook and define it for your
+configuration, with something like:
+
+@example
+#ifdef WRANGLE_SIGNALS
+ WRANGLE_SIGNALS (signo);
+#endif
+@end example
+
+In your host, target, or native configuration file, as appropriate,
+define @code{WRANGLE_SIGNALS} to do the machine-dependent thing. Take
+a bit of care in defining the hook, so that it can be used by other
+ports in the future, if they need a hook in the same place.
+
+If the hook is not defined, the code should do whatever "most" machines
+want. Using @code{#ifdef}, as above, is the preferred way to do this,
+but sometimes that gets convoluted, in which case use
+
+@example
+#ifndef SPECIAL_FOO_HANDLING
+#define SPECIAL_FOO_HANDLING(pc, sp) (0)
+#endif
+@end example
+
+where the macro is used or in an appropriate header file.
+
+Whether to include a @dfn{small} hook, a hook around the exact pieces of
+code which are system-dependent, or whether to replace a whole function
+with a hook depends on the case. A good example of this dilemma can be
+found in @code{get_saved_register}. All machines that GDB 2.8 ran on
+just needed the @code{FRAME_FIND_SAVED_REGS} hook to find the saved
+registers. Then the SPARC and Pyramid came along, and
+@code{HAVE_REGISTER_WINDOWS} and @code{REGISTER_IN_WINDOW_P} were
+introduced. Then the 29k and 88k required the @code{GET_SAVED_REGISTER}
+hook. The first three are examples of small hooks; the latter replaces
+a whole function. In this specific case, it is useful to have both
+kinds; it would be a bad idea to replace all the uses of the small hooks
+with @code{GET_SAVED_REGISTER}, since that would result in much
+duplicated code. Other times, duplicating a few lines of code here or
+there is much cleaner than introducing a large number of small hooks.
+
+Another way to generalize GDB along a particular interface is with an
+attribute struct. For example, GDB has been generalized to handle
+multiple kinds of remote interfaces -- not by #ifdef's everywhere, but
+by defining the "target_ops" structure and having a current target (as
+well as a stack of targets below it, for memory references). Whenever
+something needs to be done that depends on which remote interface we are
+using, a flag in the current target_ops structure is tested (e.g.
+`target_has_stack'), or a function is called through a pointer in the
+current target_ops structure. In this way, when a new remote interface
+is added, only one module needs to be touched -- the one that actually
+implements the new remote interface. Other examples of
+attribute-structs are BFD access to multiple kinds of object file
+formats, or GDB's access to multiple source languages.
+
+Please avoid duplicating code. For example, in GDB 3.x all the code
+interfacing between @code{ptrace} and the rest of GDB was duplicated in
+@file{*-dep.c}, and so changing something was very painful. In GDB 4.x,
+these have all been consolidated into @file{infptrace.c}.
+@file{infptrace.c} can deal with variations between systems the same way
+any system-independent file would (hooks, #if defined, etc.), and
+machines which are radically different don't need to use infptrace.c at
+all.
+
+@item
+@emph{Do} write code that doesn't depend on the sizes of C data types,
+the format of the host's floating point numbers, the alignment of anything,
+or the order of evaluation of expressions. In short, follow good
+programming practices for writing portable C code.
+
+@end table
+
+@node Submitting Patches
+@chapter Submitting Patches
+
+Thanks for thinking of offering your changes back to the community of
+GDB users. In general we like to get well designed enhancements.
+Thanks also for checking in advance about the best way to transfer the
+changes.
+
+The two main problems with getting your patches in are,
+
+@table @bullet
+@item
+The GDB maintainers will only install ``cleanly designed'' patches.
+You may not always agree on what is clean design.
+@pxref{Coding Style}, @pxref{Clean Design}.
+
+@item
+If the maintainers don't have time to put the patch in when it
+arrives, or if there is any question about a patch, it
+goes into a large queue with everyone else's patches and
+bug reports.
+@end table
+
+I don't know how to get past these problems except by continuing to try.
+
+There are two issues here -- technical and legal.
+
+The legal issue is that to incorporate substantial changes requires a
+copyright assignment from you and/or your employer, granting ownership
+of the changes to the Free Software Foundation. You can get the
+standard document for doing this by sending mail to
+@code{gnu@@prep.ai.mit.edu} and asking for it. I recommend that people
+write in "All programs owned by the Free Software Foundation" as "NAME
+OF PROGRAM", so that changes in many programs (not just GDB, but GAS,
+Emacs, GCC, etc) can be contributed with only one piece of legalese
+pushed through the bureacracy and filed with the FSF. I can't start
+merging changes until this paperwork is received by the FSF (their
+rules, which I follow since I maintain it for them).
+
+Technically, the easiest way to receive changes is to receive each
+feature as a small context diff or unidiff, suitable for "patch".
+Each message sent to me should include the changes to C code and
+header files for a single feature, plus ChangeLog entries for each
+directory where files were modified, and diffs for any changes needed
+to the manuals (gdb/doc/gdb.texi or gdb/doc/gdbint.texi). If there
+are a lot of changes for a single feature, they can be split down
+into multiple messages.
+
+In this way, if I read and like the feature, I can add it to the
+sources with a single patch command, do some testing, and check it in.
+If you leave out the ChangeLog, I have to write one. If you leave
+out the doc, I have to puzzle out what needs documenting. Etc.
+
+The reason to send each change in a separate message is that I will
+not install some of the changes. They'll be returned to you with
+questions or comments. If I'm doing my job, my message back to you
+will say what you have to fix in order to make the change acceptable.
+The reason to have separate messages for separate features is so
+that other changes (which I @emph{am} willing to accept) can be installed
+while one or more changes are being reworked. If multiple features
+are sent in a single message, I tend to not put in the effort to sort
+out the acceptable changes from the unacceptable, so none of the
+features get installed until all are acceptable.
+
+If this sounds painful or authoritarian, well, it is. But I get a lot
+of bug reports and a lot of patches, and most of them don't get
+installed because I don't have the time to finish the job that the bug
+reporter or the contributor could have done. Patches that arrive
+complete, working, and well designed, tend to get installed on the day
+they arrive. The others go into a queue and get installed if and when
+I scan back over the queue -- which can literally take months
+sometimes. It's in both our interests to make patch installation easy
+-- you get your changes installed, and I make some forward progress on
+GDB in a normal 12-hour day (instead of them having to wait until I
+have a 14-hour or 16-hour day to spend cleaning up patches before I
+can install them).
+
+Please send patches to @code{bug-gdb@@prep.ai.mit.edu}, if they are less
+than about 25,000 characters. If longer than that, either make them
+available somehow (e.g. anonymous FTP), and announce it on
+@code{bug-gdb}, or send them directly to the GDB maintainers at
+@code{gdb-patches@@cygnus.com}.
+
+@node Host Conditionals
+@chapter Host Conditionals
+
+When GDB is configured and compiled, various macros are defined or left
+undefined, to control compilation based on the attributes of the host
+system. These macros and their meanings are:
+
+@emph{NOTE: For now, both host and target conditionals are here.
+Eliminate target conditionals from this list as they are identified.}
+
+@table @code
+@item BLOCK_ADDRESS_FUNCTION_RELATIVE
+dbxread.c
+@item GDBINIT_FILENAME
+The default name of GDB's initialization file (normally @file{.gdbinit}).
+@item KERNELDEBUG
+tm-hppa.h
+@item MEM_FNS_DECLARED
+Your host config file defines this if it includes
+declarations of @code{memcpy} and @code{memset}. Define this
+to avoid conflicts between the native include
+files and the declarations in @file{defs.h}.
+@item NO_SYS_FILE
+dbxread.c
+@item PYRAMID_CONTROL_FRAME_DEBUGGING
+pyr-xdep.c
+@item SIGWINCH_HANDLER_BODY
+utils.c
+@item ADDITIONAL_OPTIONS
+main.c
+@item ADDITIONAL_OPTION_CASES
+main.c
+@item ADDITIONAL_OPTION_HANDLER
+main.c
+@item ADDITIONAL_OPTION_HELP
+main.c
+@item ADDR_BITS_REMOVE
+defs.h
+@item AIX_BUGGY_PTRACE_CONTINUE
+infptrace.c
+@item ALIGN_STACK_ON_STARTUP
+main.c
+@item ALTOS
+altos-xdep.c
+@item ALTOS_AS
+xm-altos.h
+@item ASCII_COFF
+remote-adapt.c
+@item BADMAG
+coffread.c
+@item BCS
+tm-delta88.h
+@item BEFORE_MAIN_LOOP_HOOK
+main.c
+@item BELIEVE_PCC_PROMOTION
+coffread.c
+@item BELIEVE_PCC_PROMOTION_TYPE
+stabsread.c
+@item BITS_BIG_ENDIAN
+defs.h
+@item BKPT_AT_MAIN
+solib.c
+@item BLOCK_ADDRESS_ABSOLUTE
+dbxread.c
+@item BPT_VECTOR
+tm-m68k.h
+@item BREAKPOINT
+tm-m68k.h
+@item BREAKPOINT_DEBUG
+breakpoint.c
+@item BROKEN_LARGE_ALLOCA
+Avoid large @code{alloca}'s. For example, on sun's, Large alloca's fail
+because the attempt to increase the stack limit in main() fails because
+shared libraries are allocated just below the initial stack limit. The
+SunOS kernel will not allow the stack to grow into the area occupied by
+the shared libraries.
+@item BSTRING
+regex.c
+@item CALL_DUMMY
+valops.c
+@item CALL_DUMMY_LOCATION
+inferior.h
+@item CALL_DUMMY_STACK_ADJUST
+valops.c
+@item CANNOT_FETCH_REGISTER
+hppabsd-xdep.c
+@item CANNOT_STORE_REGISTER
+findvar.c
+@item CFRONT_PRODUCER
+dwarfread.c
+@item CHILD_PREPARE_TO_STORE
+inftarg.c
+@item CLEAR_DEFERRED_STORES
+inflow.c
+@item CLEAR_SOLIB
+objfiles.c
+@item COFF_ENCAPSULATE
+hppabsd-tdep.c
+@item COFF_FORMAT
+symm-tdep.c
+@item CORE_NEEDS_RELOCATION
+stack.c
+@item CPLUS_MARKER
+cplus-dem.c
+@item CREATE_INFERIOR_HOOK
+infrun.c
+@item C_ALLOCA
+regex.c
+@item C_GLBLREG
+coffread.c
+@item DBXREAD_ONLY
+partial-stab.h
+@item DBX_PARM_SYMBOL_CLASS
+stabsread.c
+@item DEBUG
+remote-adapt.c
+@item DEBUG_INFO
+partial-stab.h
+@item DEBUG_PTRACE
+hppabsd-xdep.c
+@item DECR_PC_AFTER_BREAK
+breakpoint.c
+@item DEFAULT_PROMPT
+The default value of the prompt string (normally @code{"(gdb) "}).
+@item DELTA88
+m88k-xdep.c
+@item DEV_TTY
+symmisc.c
+@item DGUX
+m88k-xdep.c
+@item DISABLE_UNSETTABLE_BREAK
+breakpoint.c
+@item DONT_USE_REMOTE
+remote.c
+@item DO_DEFERRED_STORES
+infrun.c
+@item DO_REGISTERS_INFO
+infcmd.c
+@item EXTRACT_RETURN_VALUE
+tm-m68k.h
+@item EXTRACT_STRUCT_VALUE_ADDRESS
+values.c
+@item EXTRA_FRAME_INFO
+frame.h
+@item EXTRA_SYMTAB_INFO
+symtab.h
+@item FILES_INFO_HOOK
+target.c
+@item FLOAT_INFO
+infcmd.c
+@item FOPEN_RB
+defs.h
+@item FRAMELESS_FUNCTION_INVOCATION
+blockframe.c
+@item FRAME_ARGS_ADDRESS_CORRECT
+stack.c
+@item FRAME_CHAIN_COMBINE
+blockframe.c
+@item FRAME_CHAIN_VALID
+frame.h
+@item FRAME_CHAIN_VALID_ALTERNATE
+frame.h
+@item FRAME_FIND_SAVED_REGS
+stack.c
+@item FRAME_GET_BASEREG_VALUE
+frame.h
+@item FRAME_NUM_ARGS
+tm-m68k.h
+@item FRAME_SPECIFICATION_DYADIC
+stack.c
+@item FUNCTION_EPILOGUE_SIZE
+coffread.c
+@item F_OK
+xm-ultra3.h
+@item GCC2_COMPILED_FLAG_SYMBOL
+dbxread.c
+@item GCC_COMPILED_FLAG_SYMBOL
+dbxread.c
+@item GCC_MANGLE_BUG
+symtab.c
+@item GCC_PRODUCER
+dwarfread.c
+@item GET_SAVED_REGISTER
+findvar.c
+@item GPLUS_PRODUCER
+dwarfread.c
+@item HANDLE_RBRAC
+partial-stab.h
+@item HAVE_MMAP
+In some cases, use the system call @code{mmap} for reading symbol
+tables. For some machines this allows for sharing and quick updates.
+@item HAVE_REGISTER_WINDOWS
+findvar.c
+@item HAVE_SIGSETMASK
+main.c
+@item HAVE_TERMIO
+inflow.c
+@item HEADER_SEEK_FD
+arm-tdep.c
+@item HOSTING_ONLY
+xm-rtbsd.h
+@item HOST_BYTE_ORDER
+ieee-float.c
+@item HPUX_ASM
+xm-hp300hpux.h
+@item HPUX_VERSION_5
+hp300ux-xdep.c
+@item HP_OS_BUG
+infrun.c
+@item I80960
+remote-vx.c
+@item IEEE_DEBUG
+ieee-float.c
+@item IEEE_FLOAT
+valprint.c
+@item IGNORE_SYMBOL
+dbxread.c
+@item INIT_EXTRA_FRAME_INFO
+blockframe.c
+@item INIT_EXTRA_SYMTAB_INFO
+symfile.c
+@item INIT_FRAME_PC
+blockframe.c
+@item INNER_THAN
+valops.c
+@item INT_MAX
+defs.h
+@item INT_MIN
+defs.h
+@item IN_GDB
+i960-pinsn.c
+@item IN_SIGTRAMP
+infrun.c
+@item IN_SOLIB_TRAMPOLINE
+infrun.c
+@item ISATTY
+main.c
+@item IS_TRAPPED_INTERNALVAR
+values.c
+@item KERNELDEBUG
+dbxread.c
+@item KERNEL_DEBUGGING
+tm-ultra3.h
+@item KERNEL_U_ADDR
+Define this to the address of the @code{u} structure (the ``user struct'',
+also known as the ``u-page'') in kernel virtual memory. GDB needs to know
+this so that it can subtract this address from absolute addresses in
+the upage, that are obtained via ptrace or from core files. On systems
+that don't need this value, set it to zero.
+@item KERNEL_U_ADDR_BSD
+Define this to cause GDB to determine the address of @code{u} at runtime,
+by using Berkeley-style @code{nlist} on the kernel's image in the root
+directory.
+@item KERNEL_U_ADDR_HPUX
+Define this to cause GDB to determine the address of @code{u} at runtime,
+by using HP-style @code{nlist} on the kernel's image in the root
+directory.
+@item LCC_PRODUCER
+dwarfread.c
+@item LOG_FILE
+remote-adapt.c
+@item LONGERNAMES
+cplus-dem.c
+@item LONGEST
+defs.h
+@item CC_HAS_LONG_LONG
+defs.h
+@item PRINTF_HAS_LONG_LONG
+defs.h
+@item LONG_MAX
+defs.h
+@item LSEEK_NOT_LINEAR
+source.c
+@item L_LNNO32
+coffread.c
+@item L_SET
+This macro is used as the argument to lseek (or, most commonly, bfd_seek).
+FIXME, it should be replaced by SEEK_SET instead, which is the POSIX equivalent.
+@item MACHKERNELDEBUG
+hppabsd-tdep.c
+@item MAINTENANCE
+dwarfread.c
+@item MAINTENANCE_CMDS
+If the value of this is 1, then a number of optional maintenance commands
+are compiled in.
+@item MALLOC_INCOMPATIBLE
+Define this if the system's prototype for @code{malloc} differs from the
+@sc{ANSI} definition.
+@item MIPSEL
+mips-tdep.c
+@item MMAP_BASE_ADDRESS
+When using HAVE_MMAP, the first mapping should go at this address.
+@item MMAP_INCREMENT
+when using HAVE_MMAP, this is the increment between mappings.
+@item MONO
+ser-go32.c
+@item MOTOROLA
+xm-altos.h
+@item NBPG
+altos-xdep.c
+@item NEED_POSIX_SETPGID
+infrun.c
+@item NEED_TEXT_START_END
+exec.c
+@item NFAILURES
+regex.c
+@item NORETURN
+(in defs.h - is this really useful to define/undefine?)
+@item NOTDEF
+regex.c
+@item NOTDEF
+remote-adapt.c
+@item NOTDEF
+remote-mm.c
+@item NOTICE_SIGNAL_HANDLING_CHANGE
+infrun.c
+@item NO_HIF_SUPPORT
+remote-mm.c
+@item NO_JOB_CONTROL
+signals.h
+@item NO_MMALLOC
+GDB will use the @code{mmalloc} library for memory allocation for symbol
+reading, unless this symbol is defined. Define it on systems
+on which @code{mmalloc} does not
+work for some reason. One example is the DECstation, where its RPC
+library can't cope with our redefinition of @code{malloc} to call
+@code{mmalloc}. When defining @code{NO_MMALLOC}, you will also have
+to override the setting of @code{MMALLOC_LIB} to empty, in the Makefile.
+Therefore, this define is usually set on the command line by overriding
+@code{MMALLOC_DISABLE} in @file{config/*/*.mh}, rather than by defining
+it in @file{xm-*.h}.
+@item NO_MMALLOC_CHECK
+Define this if you are using @code{mmalloc}, but don't want the overhead
+of checking the heap with @code{mmcheck}.
+@item NO_SIGINTERRUPT
+remote-adapt.c
+@item NO_SINGLE_STEP
+infptrace.c
+@item NS32K_SVC_IMMED_OPERANDS
+ns32k-opcode.h
+@item NUMERIC_REG_NAMES
+mips-tdep.c
+@item N_SETV
+dbxread.c
+@item N_SET_MAGIC
+hppabsd-tdep.c
+@item NaN
+tm-umax.h
+@item ONE_PROCESS_WRITETEXT
+breakpoint.c
+@item O_BINARY
+exec.c
+@item O_RDONLY
+xm-ultra3.h
+@item PC
+convx-opcode.h
+@item PCC_SOL_BROKEN
+dbxread.c
+@item PC_IN_CALL_DUMMY
+inferior.h
+@item PC_LOAD_SEGMENT
+stack.c
+@item PRINT_RANDOM_SIGNAL
+infcmd.c
+@item PRINT_REGISTER_HOOK
+infcmd.c
+@item PRINT_TYPELESS_INTEGER
+valprint.c
+@item PROCESS_LINENUMBER_HOOK
+buildsym.c
+@item PROLOGUE_FIRSTLINE_OVERLAP
+infrun.c
+@item PSIGNAL_IN_SIGNAL_H
+defs.h
+@item PUSH_ARGUMENTS
+valops.c
+@item PYRAMID_CONTROL_FRAME_DEBUGGING
+pyr-xdep.c
+@item PYRAMID_CORE
+pyr-xdep.c
+@item PYRAMID_PTRACE
+pyr-xdep.c
+@item REGISTER_BYTES
+remote.c
+@item REGISTER_NAMES
+tm-a29k.h
+@item REG_STACK_SEGMENT
+exec.c
+@item REG_STRUCT_HAS_ADDR
+findvar.c
+@item RE_NREGS
+regex.h
+@item R_FP
+dwarfread.c
+@item R_OK
+xm-altos.h
+@item SEEK_END
+state.c
+@item SEEK_SET
+state.c
+@item SEM
+coffread.c
+@item SET_STACK_LIMIT_HUGE
+When defined, stack limits will be raised to their maximum. Use this
+if your host supports @code{setrlimit} and you have trouble with
+@code{stringtab} in @file{dbxread.c}.
+
+Also used in @file{fork-child.c} to return stack limits before child
+processes are forked.
+@item SHELL_COMMAND_CONCAT
+infrun.c
+@item SHELL_FILE
+infrun.c
+@item SHIFT_INST_REGS
+breakpoint.c
+@item SIGN_EXTEND_CHAR
+regex.c
+@item SIGTRAP_STOP_AFTER_LOAD
+infrun.c
+@item SKIP_PROLOGUE
+tm-m68k.h
+@item SKIP_PROLOGUE_FRAMELESS_P
+blockframe.c
+@item SKIP_TRAMPOLINE_CODE
+infrun.c
+@item SOLIB_ADD
+core.c
+@item SOLIB_CREATE_INFERIOR_HOOK
+infrun.c
+@item STACK_ALIGN
+valops.c
+@item START_INFERIOR_TRAPS_EXPECTED
+infrun.c
+@item STOP_SIGNAL
+main.c
+@item STORE_RETURN_VALUE
+tm-m68k.h
+@item SUN4_COMPILER_FEATURE
+infrun.c
+@item SUN_FIXED_LBRAC_BUG
+dbxread.c
+@item SVR4_SHARED_LIBS
+solib.c
+@item SWITCH_ENUM_BUG
+regex.c
+@item SYM1
+tm-ultra3.h
+@item SYMBOL_RELOADING_DEFAULT
+symfile.c
+@item SYNTAX_TABLE
+regex.c
+@item Sword
+regex.c
+@item TDESC
+infrun.c
+@item TIOCGETC
+inflow.c
+@item TIOCGLTC
+inflow.c
+@item TIOCGPGRP
+inflow.c
+@item TIOCLGET
+inflow.c
+@item TIOCLSET
+inflow.c
+@item TIOCNOTTY
+inflow.c
+@item T_ARG
+coffread.c
+@item T_VOID
+coffread.c
+@item UINT_MAX
+defs.h
+@item UPAGES
+altos-xdep.c
+@item USER
+m88k-tdep.c
+@item USE_GAS
+xm-news.h
+@item USE_O_NOCTTY
+inflow.c
+@item USE_STRUCT_CONVENTION
+values.c
+@item USG
+Means that System V (prior to SVR4) include files are in use.
+(FIXME: This symbol is abused in @file{infrun.c}, @file{regex.c},
+@file{remote-nindy.c}, and @file{utils.c} for other things, at the moment.)
+@item USIZE
+xm-m88k.h
+@item U_FPSTATE
+i386-xdep.c
+@item VARIABLES_INSIDE_BLOCK
+dbxread.c
+@item WRS_ORIG
+remote-vx.c
+@item _LANG_c
+language.c
+@item _LANG_m2
+language.c
+@item __GNUC__
+news-xdep.c
+@item __GO32__
+inflow.c
+@item __HPUX_ASM__
+xm-hp300hpux.h
+@item __INT_VARARGS_H
+printcmd.c
+@item __not_on_pyr_yet
+pyr-xdep.c
+@item alloca
+defs.h
+@item const
+defs.h
+@item GOULD_PN
+gould-pinsn.c
+@item hp800
+xm-hppabsd.h
+@item hpux
+hppabsd-core.c
+@item lint
+valarith.c
+@item longest_to_int
+defs.h
+@item mc68020
+m68k-stub.c
+@item notdef
+gould-pinsn.c
+@item ns32k_opcodeT
+ns32k-opcode.h
+@item sgi
+mips-tdep.c
+@item sparc
+regex.c
+@item sun
+m68k-tdep.c
+@item sun386
+tm-sun386.h
+@item test
+regex.c
+@item ultrix
+xm-mips.h
+@item volatile
+defs.h
+@end table
+
+@node Target Conditionals
+@chapter Target Conditionals
+
+When GDB is configured and compiled, various macros are defined or left
+undefined, to control compilation based on the attributes of the target
+system. These macros and their meanings are:
+
+@emph{NOTE: For now, both host and target conditionals are here.
+Eliminate host conditionals from this list as they are identified.}
+
+@table @code
+@item PUSH_DUMMY_FRAME
+Used in @samp{call_function_by_hand} to create an artificial stack frame.
+@item POP_FRAME
+Used in @samp{call_function_by_hand} to remove an artificial stack frame.
+@item BLOCK_ADDRESS_FUNCTION_RELATIVE
+dbxread.c
+@item KERNELDEBUG
+tm-hppa.h
+@item NO_SYS_FILE
+dbxread.c
+@item PYRAMID_CONTROL_FRAME_DEBUGGING
+pyr-xdep.c
+@item SIGWINCH_HANDLER_BODY
+utils.c
+@item ADDITIONAL_OPTIONS
+main.c
+@item ADDITIONAL_OPTION_CASES
+main.c
+@item ADDITIONAL_OPTION_HANDLER
+main.c
+@item ADDITIONAL_OPTION_HELP
+main.c
+@item ADDR_BITS_REMOVE
+defs.h
+@item ALIGN_STACK_ON_STARTUP
+main.c
+@item ALTOS
+altos-xdep.c
+@item ALTOS_AS
+xm-altos.h
+@item ASCII_COFF
+remote-adapt.c
+@item BADMAG
+coffread.c
+@item BCS
+tm-delta88.h
+@item BEFORE_MAIN_LOOP_HOOK
+main.c
+@item BELIEVE_PCC_PROMOTION
+coffread.c
+@item BELIEVE_PCC_PROMOTION_TYPE
+stabsread.c
+@item BITS_BIG_ENDIAN
+defs.h
+@item BKPT_AT_MAIN
+solib.c
+@item BLOCK_ADDRESS_ABSOLUTE
+dbxread.c
+@item BPT_VECTOR
+tm-m68k.h
+@item BREAKPOINT
+tm-m68k.h
+@item BREAKPOINT_DEBUG
+breakpoint.c
+@item BSTRING
+regex.c
+@item CALL_DUMMY
+valops.c
+@item CALL_DUMMY_LOCATION
+inferior.h
+@item CALL_DUMMY_STACK_ADJUST
+valops.c
+@item CANNOT_FETCH_REGISTER
+hppabsd-xdep.c
+@item CANNOT_STORE_REGISTER
+findvar.c
+@item CFRONT_PRODUCER
+dwarfread.c
+@item CHILD_PREPARE_TO_STORE
+inftarg.c
+@item CLEAR_DEFERRED_STORES
+inflow.c
+@item CLEAR_SOLIB
+objfiles.c
+@item COFF_ENCAPSULATE
+hppabsd-tdep.c
+@item COFF_FORMAT
+symm-tdep.c
+@item CORE_NEEDS_RELOCATION
+stack.c
+@item CPLUS_MARKER
+cplus-dem.c
+@item CREATE_INFERIOR_HOOK
+infrun.c
+@item C_ALLOCA
+regex.c
+@item C_GLBLREG
+coffread.c
+@item DBXREAD_ONLY
+partial-stab.h
+@item DBX_PARM_SYMBOL_CLASS
+stabsread.c
+@item DEBUG
+remote-adapt.c
+@item DEBUG_INFO
+partial-stab.h
+@item DEBUG_PTRACE
+hppabsd-xdep.c
+@item DECR_PC_AFTER_BREAK
+breakpoint.c
+@item DELTA88
+m88k-xdep.c
+@item DEV_TTY
+symmisc.c
+@item DGUX
+m88k-xdep.c
+@item DISABLE_UNSETTABLE_BREAK
+breakpoint.c
+@item DONT_USE_REMOTE
+remote.c
+@item DO_DEFERRED_STORES
+infrun.c
+@item DO_REGISTERS_INFO
+infcmd.c
+@item END_OF_TEXT_DEFAULT
+This is an expression that should designate the end of the text section
+(? FIXME ?)
+@item EXTRACT_RETURN_VALUE
+tm-m68k.h
+@item EXTRACT_STRUCT_VALUE_ADDRESS
+values.c
+@item EXTRA_FRAME_INFO
+frame.h
+@item EXTRA_SYMTAB_INFO
+symtab.h
+@item FILES_INFO_HOOK
+target.c
+@item FLOAT_INFO
+infcmd.c
+@item FOPEN_RB
+defs.h
+@item FP0_REGNUM
+a68v-xdep.c
+@item FPC_REGNUM
+mach386-xdep.c
+@item FP_REGNUM
+parse.c
+@item FPU
+Unused? 6-oct-92 rich@@cygnus.com. FIXME.
+@item FRAMELESS_FUNCTION_INVOCATION
+blockframe.c
+@item FRAME_ARGS_ADDRESS_CORRECT
+stack.c
+@item FRAME_CHAIN
+Given FRAME, return a pointer to the calling frame.
+@item FRAME_CHAIN_COMBINE
+blockframe.c
+@item FRAME_CHAIN_VALID
+frame.h
+@item FRAME_CHAIN_VALID_ALTERNATE
+frame.h
+@item FRAME_FIND_SAVED_REGS
+stack.c
+@item FRAME_GET_BASEREG_VALUE
+frame.h
+@item FRAME_NUM_ARGS
+tm-m68k.h
+@item FRAME_SPECIFICATION_DYADIC
+stack.c
+@item FRAME_SAVED_PC
+Given FRAME, return the pc saved there. That is, the return address.
+@item FUNCTION_EPILOGUE_SIZE
+coffread.c
+@item F_OK
+xm-ultra3.h
+@item GCC2_COMPILED_FLAG_SYMBOL
+dbxread.c
+@item GCC_COMPILED_FLAG_SYMBOL
+dbxread.c
+@item GCC_MANGLE_BUG
+symtab.c
+@item GCC_PRODUCER
+dwarfread.c
+@item GDB_TARGET_IS_HPPA
+This determines whether horrible kludge code in dbxread.c and partial-stab.h
+is used to mangle multiple-symbol-table files from HPPA's. This should all
+be ripped out, and a scheme like elfread.c used.
+@item GDB_TARGET_IS_MACH386
+mach386-xdep.c
+@item GDB_TARGET_IS_SUN3
+a68v-xdep.c
+@item GDB_TARGET_IS_SUN386
+sun386-xdep.c
+@item GET_LONGJMP_TARGET
+For most machines, this is a target-dependent parameter. On the DECstation
+and the Iris, this is a native-dependent parameter, since <setjmp.h> is
+needed to define it.
+
+This macro determines the target PC address that longjmp() will jump
+to, assuming that we have just stopped at a longjmp breakpoint. It
+takes a CORE_ADDR * as argument, and stores the target PC value through
+this pointer. It examines the current state of the machine as needed.
+@item GET_SAVED_REGISTER
+findvar.c
+@item GPLUS_PRODUCER
+dwarfread.c
+@item GR64_REGNUM
+remote-adapt.c
+@item GR64_REGNUM
+remote-mm.c
+@item HANDLE_RBRAC
+partial-stab.h
+@item HAVE_68881
+m68k-tdep.c
+@item HAVE_REGISTER_WINDOWS
+findvar.c
+@item HAVE_SIGSETMASK
+main.c
+@item HAVE_TERMIO
+inflow.c
+@item HEADER_SEEK_FD
+arm-tdep.c
+@item HOSTING_ONLY
+xm-rtbsd.h
+@item HOST_BYTE_ORDER
+ieee-float.c
+@item HPUX_ASM
+xm-hp300hpux.h
+@item HPUX_VERSION_5
+hp300ux-xdep.c
+@item HP_OS_BUG
+infrun.c
+@item I80960
+remote-vx.c
+@item IBM6000_TARGET
+Shows that we are configured for an IBM RS/6000 target. This conditional
+should be eliminated (FIXME) and replaced by feature-specific macros.
+It was introduced in haste and we are repenting at leisure.
+@item IEEE_DEBUG
+ieee-float.c
+@item IEEE_FLOAT
+valprint.c
+@item IGNORE_SYMBOL
+dbxread.c
+@item INIT_EXTRA_FRAME_INFO
+blockframe.c
+@item INIT_EXTRA_SYMTAB_INFO
+symfile.c
+@item INIT_FRAME_PC
+blockframe.c
+@item INNER_THAN
+valops.c
+@item INT_MAX
+defs.h
+@item INT_MIN
+defs.h
+@item IN_GDB
+i960-pinsn.c
+@item IN_SIGTRAMP
+infrun.c
+@item IN_SOLIB_TRAMPOLINE
+infrun.c
+@item ISATTY
+main.c
+@item IS_TRAPPED_INTERNALVAR
+values.c
+@item KERNELDEBUG
+dbxread.c
+@item KERNEL_DEBUGGING
+tm-ultra3.h
+@item LCC_PRODUCER
+dwarfread.c
+@item LOG_FILE
+remote-adapt.c
+@item LONGERNAMES
+cplus-dem.c
+@item LONGEST
+defs.h
+@item CC_HAS_LONG_LONG
+defs.h
+@item PRINTF_HAS_LONG_LONG
+defs.h
+@item LONG_MAX
+defs.h
+@item L_LNNO32
+coffread.c
+@item MACHKERNELDEBUG
+hppabsd-tdep.c
+@item MAINTENANCE
+dwarfread.c
+@item MIPSEL
+mips-tdep.c
+@item MOTOROLA
+xm-altos.h
+@item NBPG
+altos-xdep.c
+@item NEED_POSIX_SETPGID
+infrun.c
+@item NEED_TEXT_START_END
+exec.c
+@item NFAILURES
+regex.c
+@item NNPC_REGNUM
+infrun.c
+@item NOTDEF
+regex.c
+@item NOTDEF
+remote-adapt.c
+@item NOTDEF
+remote-mm.c
+@item NOTICE_SIGNAL_HANDLING_CHANGE
+infrun.c
+@item NO_HIF_SUPPORT
+remote-mm.c
+@item NO_SIGINTERRUPT
+remote-adapt.c
+@item NO_SINGLE_STEP
+infptrace.c
+@item NPC_REGNUM
+infcmd.c
+@item NS32K_SVC_IMMED_OPERANDS
+ns32k-opcode.h
+@item NUMERIC_REG_NAMES
+mips-tdep.c
+@item N_SETV
+dbxread.c
+@item N_SET_MAGIC
+hppabsd-tdep.c
+@item NaN
+tm-umax.h
+@item ONE_PROCESS_WRITETEXT
+breakpoint.c
+@item PC
+convx-opcode.h
+@item PCC_SOL_BROKEN
+dbxread.c
+@item PC_IN_CALL_DUMMY
+inferior.h
+@item PC_LOAD_SEGMENT
+stack.c
+@item PC_REGNUM
+parse.c
+@item PRINT_RANDOM_SIGNAL
+infcmd.c
+@item PRINT_REGISTER_HOOK
+infcmd.c
+@item PRINT_TYPELESS_INTEGER
+valprint.c
+@item PROCESS_LINENUMBER_HOOK
+buildsym.c
+@item PROLOGUE_FIRSTLINE_OVERLAP
+infrun.c
+@item PSIGNAL_IN_SIGNAL_H
+defs.h
+@item PS_REGNUM
+parse.c
+@item PUSH_ARGUMENTS
+valops.c
+@item REGISTER_BYTES
+remote.c
+@item REGISTER_NAMES
+tm-a29k.h
+@item REG_STACK_SEGMENT
+exec.c
+@item REG_STRUCT_HAS_ADDR
+findvar.c
+@item RE_NREGS
+regex.h
+@item R_FP
+dwarfread.c
+@item R_OK
+xm-altos.h
+@item SDB_REG_TO_REGNUM
+Define this to convert sdb register numbers
+into gdb regnums. If not defined, no conversion will be done.
+@item SEEK_END
+state.c
+@item SEEK_SET
+state.c
+@item SEM
+coffread.c
+@item SHELL_COMMAND_CONCAT
+infrun.c
+@item SHELL_FILE
+infrun.c
+@item SHIFT_INST_REGS
+breakpoint.c
+@item SIGN_EXTEND_CHAR
+regex.c
+@item SIGTRAP_STOP_AFTER_LOAD
+infrun.c
+@item SKIP_PROLOGUE
+tm-m68k.h
+@item SKIP_PROLOGUE_FRAMELESS_P
+blockframe.c
+@item SKIP_TRAMPOLINE_CODE
+infrun.c
+@item SOLIB_ADD
+core.c
+@item SOLIB_CREATE_INFERIOR_HOOK
+infrun.c
+@item SP_REGNUM
+parse.c
+@item STAB_REG_TO_REGNUM
+Define this to convert stab register numbers (as gotten from `r' declarations)
+into gdb regnums. If not defined, no conversion will be done.
+@item STACK_ALIGN
+valops.c
+@item START_INFERIOR_TRAPS_EXPECTED
+infrun.c
+@item STOP_SIGNAL
+main.c
+@item STORE_RETURN_VALUE
+tm-m68k.h
+@item SUN4_COMPILER_FEATURE
+infrun.c
+@item SUN_FIXED_LBRAC_BUG
+dbxread.c
+@item SVR4_SHARED_LIBS
+solib.c
+@item SWITCH_ENUM_BUG
+regex.c
+@item SYM1
+tm-ultra3.h
+@item SYMBOL_RELOADING_DEFAULT
+symfile.c
+@item SYNTAX_TABLE
+regex.c
+@item Sword
+regex.c
+@item TARGET_BYTE_ORDER
+defs.h
+@item TARGET_CHAR_BIT
+defs.h
+@item TARGET_COMPLEX_BIT
+defs.h
+@item TARGET_DOUBLE_BIT
+defs.h
+@item TARGET_DOUBLE_COMPLEX_BIT
+defs.h
+@item TARGET_FLOAT_BIT
+defs.h
+@item TARGET_INT_BIT
+defs.h
+@item TARGET_LONG_BIT
+defs.h
+@item TARGET_LONG_DOUBLE_BIT
+defs.h
+@item TARGET_LONG_LONG_BIT
+defs.h
+@item TARGET_PTR_BIT
+defs.h
+@item TARGET_READ_PC
+@item TARGET_WRITE_PC
+@item TARGET_READ_SP
+@item TARGET_WRITE_SP
+@item TARGET_READ_FP
+@item TARGET_WRITE_FP
+These change the behavior of @code{read_pc}, @code{write_pc},
+@code{read_sp}, @code{write_sp}, @code{read_fp} and @code{write_fp}.
+For most targets, these may be left undefined. GDB will call the
+read and write register functions with the relevant @code{_REGNUM} argument.
+
+These macros are useful when a target keeps one of these registers in a
+hard to get at place; for example, part in a segment register and part
+in an ordinary register.
+
+@item TARGET_SHORT_BIT
+defs.h
+@item TDESC
+infrun.c
+@item T_ARG
+coffread.c
+@item T_VOID
+coffread.c
+@item UINT_MAX
+defs.h
+@item USER
+m88k-tdep.c
+@item USE_GAS
+xm-news.h
+@item USE_STRUCT_CONVENTION
+values.c
+@item USIZE
+xm-m88k.h
+@item U_FPSTATE
+i386-xdep.c
+@item VARIABLES_INSIDE_BLOCK
+dbxread.c
+@item WRS_ORIG
+remote-vx.c
+@item _LANG_c
+language.c
+@item _LANG_m2
+language.c
+@item __GO32__
+inflow.c
+@item __HPUX_ASM__
+xm-hp300hpux.h
+@item __INT_VARARGS_H
+printcmd.c
+@item __not_on_pyr_yet
+pyr-xdep.c
+@item GOULD_PN
+gould-pinsn.c
+@item hp800
+xm-hppabsd.h
+@item hpux
+hppabsd-core.c
+@item longest_to_int
+defs.h
+@item mc68020
+m68k-stub.c
+@item ns32k_opcodeT
+ns32k-opcode.h
+@item sgi
+mips-tdep.c
+@item sparc
+regex.c
+@item sun
+m68k-tdep.c
+@item sun386
+tm-sun386.h
+@item test
+(Define this to enable testing code in regex.c.)
+@end table
+
+@node Native Conditionals
+@chapter Native Conditionals
+
+When GDB is configured and compiled, various macros are defined or left
+undefined, to control compilation when the host and target systems
+are the same. These macros should be defined (or left undefined)
+in @file{nm-@var{system}.h}.
+
+@table @code
+@item ATTACH_DETACH
+If defined, then gdb will include support for the @code{attach} and
+@code{detach} commands.
+@item FETCH_INFERIOR_REGISTERS
+Define this if the native-dependent code will provide its
+own routines
+@code{fetch_inferior_registers} and @code{store_inferior_registers} in
+@file{@var{HOST}-nat.c}.
+If this symbol is @emph{not} defined, and @file{infptrace.c}
+is included in this configuration, the default routines in
+@file{infptrace.c} are used for these functions.
+@item GET_LONGJMP_TARGET
+For most machines, this is a target-dependent parameter. On the DECstation
+and the Iris, this is a native-dependent parameter, since <setjmp.h> is
+needed to define it.
+
+This macro determines the target PC address that longjmp() will jump
+to, assuming that we have just stopped at a longjmp breakpoint. It
+takes a CORE_ADDR * as argument, and stores the target PC value through
+this pointer. It examines the current state of the machine as needed.
+@item PROC_NAME_FMT
+Defines the format for the name of a @file{/proc} device. Should be
+defined in @file{nm.h} @emph{only} in order to override the default
+definition in @file{procfs.c}.
+@item PTRACE_FP_BUG
+mach386-xdep.c
+@item PTRACE_ARG3_TYPE
+The type of the third argument to the @code{ptrace} system call, if it exists
+and is different from @code{int}.
+@item REGISTER_U_ADDR
+Defines the offset of the registers in the ``u area''; @pxref{Host}.
+@item USE_PROC_FS
+This determines whether small routines in @file{*-tdep.c}, which
+translate register values
+between GDB's internal representation and the /proc representation,
+are compiled.
+@item U_REGS_OFFSET
+This is the offset of the registers in the upage. It need only be
+defined if the generic ptrace register access routines in
+@file{infptrace.c} are being used (that is,
+@file{infptrace.c} is configured in, and
+@code{FETCH_INFERIOR_REGISTERS} is not defined). If the default value
+from @file{infptrace.c} is good enough, leave it undefined.
+
+The default value means that u.u_ar0 @emph{points to} the location of the
+registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means that
+u.u_ar0 @emph{is} the location of the registers.
+@end table
+
+@node Obsolete Conditionals
+@chapter Obsolete Conditionals
+
+Fragments of old code in GDB sometimes reference or set the following
+configuration macros. They should not be used by new code, and
+old uses should be removed as those parts of the debugger are
+otherwise touched.
+
+@table @code
+@item STACK_END_ADDR
+This macro used to define where the end of the stack appeared, for use
+in interpreting core file formats that don't record this address in the
+core file itself. This information is now configured in BFD, and GDB
+gets the info portably from there. The values in GDB's configuration
+files should be moved into BFD configuration files (if needed there),
+and deleted from all of GDB's config files.
+
+Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
+is so old that it has never been converted to use BFD. Now that's old!
+@end table
+
+@node XCOFF
+@chapter The XCOFF Object File Format
+
+The IBM RS/6000 running AIX uses an object file format called xcoff.
+The COFF sections, symbols, and line numbers are used, but debugging
+symbols are dbx-style stabs whose strings are located in the
+@samp{.debug} section (rather than the string table). For more
+information, @xref{Top,,,stabs,The Stabs Debugging Format}, and search
+for XCOFF.
+
+The shared library scheme has a nice clean interface for figuring out
+what shared libraries are in use, but the catch is that everything which
+refers to addresses (symbol tables and breakpoints at least) needs to be
+relocated for both shared libraries and the main executable. At least
+using the standard mechanism this can only be done once the program has
+been run (or the core file has been read).
+
+@contents
+@bye