binutils-gdb/gdb/doc/gdbint.texinfo

\input texinfo
@setfilename gdbint.info
@c $Id$

@ifinfo
@format
START-INFO-DIR-ENTRY
* Gdb-Internals: (gdbint).	The GNU debugger internals.
END-INFO-DIR-ENTRY
@end format
@end ifinfo

@ifinfo
This file documents the internals of the GNU debugger GDB.

Copyright (C) 1990, 1991, 1992 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$}  % 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 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, README, (dir), (dir)

This file documents the internals of the GNU debugger GDB.  It is a
collection of miscellaneous information with little form at this point.
Mostly, it is a repository into which you can put information about
GDB as you discover it (or as you design changes to GDB).

@menu
* README::			The README File
* New Architectures::		Defining a New Host or Target Architecture
* Config::			Adding a New Configuration
* Host::			Adding a New Host
* 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
* 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
* Host Conditionals::           Controlling what features exist in the host
* Target Conditionals::         Controlling what features exist in the target

@end menu

@node README, New Architectures, Top, Top
@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 New Architectures, Config, README, Top
@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; unfortunately, that
means you must add @emph{both} host and target support for new machines
in this category.

The @file{config/mh-*}, @file{xm-*.h} and @file{*-xdep.c} files are for
host support.  Similarly, the @file{config/mt-*}, @file{tm-*.h} and
@file{*-tdep.c} files are for target support.  The question is, what
features or aspects of a debugging or cross-debugging environment are
considered to be ``host'' support?

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.

Unix child process support is considered an aspect of the host.  Since
when you fork on the host you are still on the host, the various macros
needed for finding the registers in the upage, running @code{ptrace}, and such
are all in the host-dependent files.

@c FIXME so what kinds of things are target support?

This is still somewhat of a grey area; I (John Gilmore) didn't do the
@file{xm-*} and @file{tm-*} split for gdb (it was done by Jim Kingdon)
so I have had to figure out the grounds on which it was split, and make
my own choices as I evolve it.  I have moved many things out of the xdep
files actually, partly as a result of BFD and partly by removing
duplicated code.


@node Config, Host, New Architectures, Top
@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 GDB.

Then edit @file{bfd/configure.in}.  Add shell script code 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.

Also, if this host requires any changes to the Makefile, create a file
@file{bfd/config/mh-@var{xxx}}, which includes the required lines.

(If you have the binary utilities and/or GNU ld in the same tree,
you'll also have to edit @file{binutils/configure.in} or
@file{ld/configure.in} to match what you've done in the @file{bfd}
directory.)

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}.

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- and
target-dependent @file{.h} and @file{.c} files used for your
configuration; the next two chapters discuss those.


@node Host, Target, Config, Top
@chapter Adding a New Host

Once you have specified a new configuration for your host
(@pxref{Config,,Adding a New Configuration}), there are two 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}

Several files control GDB's configuration for host systems:

@table @file
@item gdb/config/mh-@var{xxx}
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
@samp{XM_FILE= xm-@var{xxx}.h}.  You can also define @samp{CC},
@samp{REGEX} and @samp{REGEX1}, @samp{SYSV_DEFINE}, @samp{XM_CFLAGS},
@samp{XM_ADD_FILES}, @samp{XM_CLIBS}, @samp{XM_CDEPS},
etc.; see @file{Makefile.in}.

@item gdb/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 some machines it doesn't exist at all.
@end table

There are some ``generic'' versions of routines that can be used by
various host 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}.  

@subheading Generic Host Support Files

@table @file

@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}-xdep.c} (or @code{REGISTER_U_ADDR} in @code{xm-@var{xxx}.h}).

@item coredep.c::register_addr()
If your @code{xm-@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}-xdep.c} file, and be sure @code{@var{xxx}-xdep.o} is in
the @code{XDEPFILES} 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

Object files needed when the target system is an @var{xxx} are listed
in the file @file{config/mt-@var{xxx}}, in the makefile macro
@samp{TDEPFILES = }@dots{}.  The header file that defines the target
system should be called @file{tm-@var{xxx}.h}, and should be specified
as the value of @samp{TM_FILE} in @file{config/mt-@var{xxx}}.  You can
also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, and @samp{TM_CDEPS} in
there; see @file{Makefile.in}.

Now, you are now ready to try configuring GDB to compile for your system.
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

Good luck!  Comments and suggestions about this section are particularly
welcome; send them to @samp{bug-gdb@@prep.ai.mit.edu}.

When hosting GDB 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{core-dep.c}; if not, it's in your @file{@var{xxx}-xdep.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.)


@node Target, Languages, Host, Top
@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/mt-@var{ttt}
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},
and other Makefile variables here; see @file{Makefile.in}.

@item gdb/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/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 are beyond the scope
of this document right now.  Look at the structure of the a.out
and COFF support, build a transfer vector (@code{xvec}) for your new format,
and start populating it with routines.  Add it to the list in
@file{bfd/targets.c}.

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, Releases, Target, Top
@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, Partial Symbol Tables, Languages, Top
@chapter Configuring GDB for Release

From the top level directory (containing @file{gdb}, @file{bfd},
@file{libiberty}, and so on):
@example
make 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.

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, BFD support for GDB, Releases, Top
@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 BFD support for GDB, Symbol Reading, Partial Symbol Tables, Top
@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, Cleanups, BFD support for GDB, Top
@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, Wrapping, Symbol Reading, Top
@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 @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, Frames, Cleanups, Top
@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,  , Wrapping, Top
@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 Host Conditionals,  , , Top
@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 ALIGN_SIZE
alloca.c
@item BLOCK_ADDRESS_FUNCTION_RELATIVE
dbxread.c
@item GDBINIT_FILENAME
main.c
@item KERNELDEBUG
tm-hppa.h
@item MEM_FNS_DECLARED
defs.h
@item NO_SYS_FILE
dbxread.c
@item USE_PROC_FS
sparc-tdep.c
@item PYRAMID_CONTROL_FRAME_DEBUGGING
pyr-xdep.c
@item SIGWINCH_HANDLER_BODY
utils.c
@item 1
buildsym.c
@item 1
dbxread.c
@item 1
dbxread.c
@item 1
buildsym.c
@item 1
dwarfread.c
@item 1
valops.c
@item 1
valops.c
@item 1
pyr-xdep.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 ATTACH_DETACH
hppabsd-xdep.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 BIG_ENDIAN
defs.h
@item BITS_BIG_ENDIAN
defs.h
@item BKPT_AT_MAIN
solib.c
@item BLOCK_ADDRESS_ABSOLUTE
dbxread.c
@item BPT_VECTOR
tm-68k.h
@item BREAKPOINT
tm-68k.h
@item BREAKPOINT_DEBUG
breakpoint.c
@item BROKEN_LARGE_ALLOCA
source.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 COFF_NO_LONG_FILE_NAMES
coffread.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 DAMON
xcoffexec.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
main.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
dbxread.c
@item EXTERN
buildsym.h
@item EXTRACT_RETURN_VALUE
tm-68k.h
@item EXTRACT_STRUCT_VALUE_ADDRESS
values.c
@item EXTRA_FRAME_INFO
frame.h
@item EXTRA_SYMTAB_INFO
symtab.h
@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}.
If this symbol is @emph{not} defined, the default routines in
@file{infptrace.c} are used for these functions.
@item FILES_INFO_HOOK
target.c
@item FIXME
coffread.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 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-68k.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 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
i386-tdep.c
@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_MMAP
state.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_HOST
breakpoint.c
@item IBM6000_TARGET
buildsym.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 LITTLE_ENDIAN
defs.h
@item LOG_FILE
remote-adapt.c
@item LONGERNAMES
cplus-dem.c
@item LONGEST
defs.h
@item LONG_LONG
defs.h
@item LONG_MAX
defs.h
@item LSEEK_NOT_LINEAR
source.c
@item L_LNNO32
coffread.c
@item L_SET
xm-ultra3.h
@item MACHKERNELDEBUG
hppabsd-tdep.c
@item MAIN
cplus-dem.c
@item MAINTENANCE
dwarfread.c
@item MAINTENANCE_CMDS
breakpoint.c
@item MAINTENANCE_CMDS
maint.c
@item MALLOC_INCOMPATIBLE
defs.h
@item MIPSEL
mips-tdep.c
@item MMAP_BASE_ADDRESS
objfiles.c
@item MONO
ser-go32.c
@item MOTOROLA
xm-altos.h
@item NAMES_HAVE_UNDERSCORE
coffread.c
@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 NORETURN
defs.h
@item NOTDEF
regex.c
@item NOTDEF
remote-adapt.c
@item NOTDEF
remote-mm.c
@item NOTICE_SIGNAL_HANDLING_CHANGE
infrun.c
@item NO_DEFINE_SYMBOL
xcoffread.c
@item NO_HIF_SUPPORT
remote-mm.c
@item NO_JOB_CONTROL
signals.h
@item NO_MALLOC_CHECK
utils.c
@item NO_MMALLOC
utils.c
@item NO_MMALLOC
objfiles.c
@item NO_MMALLOC
utils.c
@item NO_SIGINTERRUPT
remote-adapt.c
@item NO_SINGLE_STEP
infptrace.c
@item NO_TYPEDEFS
xcoffread.c
@item NO_TYPEDEFS
xcoffread.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 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 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 PTRACE_ARG3_TYPE
inferior.h
@item PTRACE_FP_BUG
mach386-xdep.c
@item PT_ATTACH
hppabsd-xdep.c
@item PT_DETACH
hppabsd-xdep.c
@item PT_KILL
infptrace.c
@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-29k.h
@item REGISTER_U_ADDR
Defines the offset of the registers in the ``u area''; @pxref{Host}.
@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
coffread.c
@item SEEK_END
state.c
@item SEEK_SET
state.c
@item SEM
coffread.c
@item SET_STACK_LIMIT_HUGE
infrun.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-68k.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 SOME_NAMES_HAVE_DOT
minsyms.c
@item SP_REGNUM
parse.c
@item STAB_REG_TO_REGNUM
stabsread.h
@item STACK_ALIGN
valops.c
@item STACK_DIRECTION
alloca.c
@item START_INFERIOR_TRAPS_EXPECTED
infrun.c
@item STOP_SIGNAL
main.c
@item STORE_RETURN_VALUE
tm-68k.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 TM_FILE_OVERRIDE
defs.h
@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_PROC_FS
inferior.h
@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 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, @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.
@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 __HAVE_68881__
m68k-stub.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 emacs
alloca.c
@item hp800
xm-hppabsd.h
@item hp9000s800
dbxread.c
@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 static
alloca.c
@item sun
m68k-tdep.c
@item sun386
tm-sun386.h
@item test
regex.c
@item ultrix
xm-mips.h
@item volatile
defs.h
@item x_name
coffread.c
@item x_zeroes
coffread.c
@end table

@node Target Conditionals,  , , Top
@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 ALIGN_SIZE
alloca.c
@item BLOCK_ADDRESS_FUNCTION_RELATIVE
dbxread.c
@item GDBINIT_FILENAME
main.c
@item KERNELDEBUG
tm-hppa.h
@item MEM_FNS_DECLARED
defs.h
@item NO_SYS_FILE
dbxread.c
@item USE_PROC_FS
sparc-tdep.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 ATTACH_DETACH
hppabsd-xdep.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 BIG_ENDIAN
defs.h
@item BITS_BIG_ENDIAN
defs.h
@item BKPT_AT_MAIN
solib.c
@item BLOCK_ADDRESS_ABSOLUTE
dbxread.c
@item BPT_VECTOR
tm-68k.h
@item BREAKPOINT
tm-68k.h
@item BREAKPOINT_DEBUG
breakpoint.c
@item BROKEN_LARGE_ALLOCA
source.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 COFF_NO_LONG_FILE_NAMES
coffread.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 DAMON
xcoffexec.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
main.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
dbxread.c
@item EXTERN
buildsym.h
@item EXTRACT_RETURN_VALUE
tm-68k.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 FIXME
coffread.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 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-68k.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 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
i386-tdep.c
@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_MMAP
state.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_HOST
breakpoint.c
@item IBM6000_TARGET
buildsym.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 LCC_PRODUCER
dwarfread.c
@item LITTLE_ENDIAN
defs.h
@item LOG_FILE
remote-adapt.c
@item LONGERNAMES
cplus-dem.c
@item LONGEST
defs.h
@item LONG_LONG
defs.h
@item LONG_MAX
defs.h
@item LSEEK_NOT_LINEAR
source.c
@item L_LNNO32
coffread.c
@item L_SET
xm-ultra3.h
@item MACHKERNELDEBUG
hppabsd-tdep.c
@item MAIN
cplus-dem.c
@item MAINTENANCE
dwarfread.c
@item MAINTENANCE_CMDS
breakpoint.c
@item MAINTENANCE_CMDS
maint.c
@item MIPSEL
mips-tdep.c
@item MMAP_BASE_ADDRESS
objfiles.c
@item MOTOROLA
xm-altos.h
@item NAMES_HAVE_UNDERSCORE
coffread.c
@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 NORETURN
defs.h
@item NOTDEF
regex.c
@item NOTDEF
remote-adapt.c
@item NOTDEF
remote-mm.c
@item NOTICE_SIGNAL_HANDLING_CHANGE
infrun.c
@item NO_DEFINE_SYMBOL
xcoffread.c
@item NO_HIF_SUPPORT
remote-mm.c
@item NO_JOB_CONTROL
signals.h
@item NO_MALLOC_CHECK
utils.c
@item NO_MMALLOC
utils.c
@item NO_MMALLOC
objfiles.c
@item NO_MMALLOC
utils.c
@item NO_SIGINTERRUPT
remote-adapt.c
@item NO_SINGLE_STEP
infptrace.c
@item NO_TYPEDEFS
xcoffread.c
@item NO_TYPEDEFS
xcoffread.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 PTRACE_ARG3_TYPE
inferior.h
@item PTRACE_FP_BUG
mach386-xdep.c
@item PUSH_ARGUMENTS
valops.c
@item REGISTER_BYTES
remote.c
@item REGISTER_NAMES
tm-29k.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
coffread.c
@item SEEK_END
state.c
@item SEEK_SET
state.c
@item SEM
coffread.c
@item SET_STACK_LIMIT_HUGE
infrun.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-68k.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 SOME_NAMES_HAVE_DOT
minsyms.c
@item SP_REGNUM
parse.c
@item STAB_REG_TO_REGNUM
stabsread.h
@item STACK_ALIGN
valops.c
@item STACK_DIRECTION
alloca.c
@item START_INFERIOR_TRAPS_EXPECTED
infrun.c
@item STOP_SIGNAL
main.c
@item STORE_RETURN_VALUE
tm-68k.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_SHORT_BIT
defs.h
@item TDESC
infrun.c
@item TM_FILE_OVERRIDE
defs.h
@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 __HAVE_68881__
m68k-stub.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 emacs
alloca.c
@item hp800
xm-hppabsd.h
@item hp9000s800
dbxread.c
@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 static
alloca.c
@item sun
m68k-tdep.c
@item sun386
tm-sun386.h
@item test
regex.c
@item x_name
coffread.c
@item x_zeroes
coffread.c
@end table

@contents
@bye