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Diffstat (limited to 'contrib/gcc/doc/hostconfig.texi')
| -rw-r--r-- | contrib/gcc/doc/hostconfig.texi | 212 |
1 files changed, 143 insertions, 69 deletions
diff --git a/contrib/gcc/doc/hostconfig.texi b/contrib/gcc/doc/hostconfig.texi index 33c0a3b..5c38313 100644 --- a/contrib/gcc/doc/hostconfig.texi +++ b/contrib/gcc/doc/hostconfig.texi @@ -1,72 +1,119 @@ -@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -@c 1999, 2000, 2001, 2002 Free Software Foundation, Inc. +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, +@c 2000, 2001, 2002, 2003 Free Software Foundation, Inc. @c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. +@c For copying conditions, see the file gccint.texi. @node Host Config -@chapter Host Configuration Headers +@chapter Host Configuration +@cindex host configuration + +Most details about the machine and system on which the compiler is +actually running are detected by the @command{configure} script. Some +things are impossible for @command{configure} to detect; these are +described in two ways, either by macros defined in a file named +@file{xm-@var{machine}.h} or by hook functions in the file specified +by the @var{out_host_hook_obj} variable in @file{config.gcc}. (The +intention is that very few hosts will need a header file but nearly +every fully supported host will need to override some hooks.) + +If you need to define only a few macros, and they have simple +definitions, consider using the @code{xm_defines} variable in your +@file{config.gcc} entry instead of creating a host configuration +header. @xref{System Config}. + +@menu +* Host Common:: Things every host probably needs implemented. +* Filesystem:: Your host can't have the letter `a' in filenames? +* Host Misc:: Rare configuration options for hosts. +@end menu + +@node Host Common +@section Host Common +@cindex host hooks +@cindex host functions + +Some things are just not portable, even between similar operating systems, +and are too difficult for autoconf to detect. They get implemented using +hook functions in the file specified by the @var{host_hook_obj} +variable in @file{config.gcc}. + +@deftypefn {Host Hook} void HOST_HOOKS_EXTRA_SIGNALS (void) +This host hook is used to set up handling for extra signals. The most +common thing to do in this hook is to detect stack overflow. +@end deftypefn + +@deftypefn {Host Hook} void * HOST_HOOKS_GT_PCH_GET_ADDRESS (size_t @var{size}) +This host hook returns the address of some space in which a PCH may be +loaded with @samp{HOST_HOOKS_PCH_LOAD_PCH}. The space will need to +have @var{size} bytes. If insufficient space is available, +@samp{NULL} may be returned; the PCH machinery will try to find a +suitable address using a heuristic. + +The memory does not have to be available now. In fact, usually +@samp{HOST_HOOKS_PCH_LOAD_PCH} will already have been called. The memory +need only be available in future invocations of GCC. +@end deftypefn + +@deftypefn {Host Hook} bool HOST_HOOKS_GT_PCH_USE_ADDRESS (size_t @var{size}, void * @var{address}) +This host hook is called when a PCH file is about to be loaded. If +@var{address} is the address that would have been returned by +@samp{HOST_HOOKS_PCH_MEMORY_ADDRESS}, and @var{size} is smaller than +the maximum than @samp{HOST_HOOKS_PCH_MEMORY_ADDRESS} would have +accepted, return true, otherwise return false. + +In addition, free any address space reserved that isn't needed to hold +@var{size} bytes (whether or not true is returned). The PCH machinery will +use @samp{mmap} with @samp{MAP_FIXED} to load the PCH if @samp{HAVE_MMAP_FILE}, +or will use @samp{fread} otherwise. + +If no PCH will be loaded, this hook may be called with @var{size} +zero, in which case all reserved address space should be freed. + +Do not try to handle values of @var{address} that could not have been +returned by this executable; just return false. Such values usually +indicate an out-of-date PCH file (built by some other GCC executable), +and such a PCH file won't work. +@end deftypefn + +@node Filesystem +@section Host Filesystem @cindex configuration file @cindex @file{xm-@var{machine}.h} -Host configuration headers contain macro definitions that describe the -machine and system on which the compiler is running. They are usually -unnecessary. Most of the things GCC needs to know about the host -system can be deduced by the @command{configure} script. - -If your host does need a special configuration header, it should be -named @file{xm-@var{machine}.h}, where @var{machine} is a short mnemonic -for the machine. Here are some macros which this header can define. +GCC needs to know a number of things about the semantics of the host +machine's filesystem. Filesystems with Unix and MS-DOS semantics are +automatically detected. For other systems, you can define the +following macros in @file{xm-@var{machine}.h}. @ftable @code -@item VMS -Define this macro if the host system is VMS@. - -@item FATAL_EXIT_CODE -A C expression for the status code to be returned when the compiler -exits after serious errors. The default is the system-provided macro -@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that -macro. Define this macro only if these defaults are incorrect. - -@item SUCCESS_EXIT_CODE -A C expression for the status code to be returned when the compiler -exits without serious errors. (Warnings are not serious errors.) The -default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if -the system doesn't define that macro. Define this macro only if these -defaults are incorrect. - -@item USE_C_ALLOCA -Define this macro if GCC should use the C implementation of @code{alloca} -provided by @file{libiberty.a}. This only affects how some parts of the -compiler itself allocate memory. It does not change code generation. - -When GCC is built with a compiler other than itself, the C @code{alloca} -is always used. This is because most other implementations have serious -bugs. You should define this macro only on a system where no -stack-based @code{alloca} can possibly work. For instance, if a system -has a small limit on the size of the stack, GCC's builtin @code{alloca} -will not work reliably. - @item HAVE_DOS_BASED_FILE_SYSTEM -Define this macro if the host file system obeys the semantics defined by -MS-DOS instead of Unix. DOS file systems are case insensitive, file -specifications may begin with a drive letter, and both forward slash and -backslash (@samp{/} and @samp{\}) are directory separators. If you -define this macro, you probably need to define the next three macros too. - -@item PATH_SEPARATOR -If defined, this macro should expand to a character constant specifying -the separator for elements of search paths. The default value is a -colon (@samp{:}). DOS-based systems usually use semicolon (@samp{;}). +This macro is automatically defined by @file{system.h} if the host +file system obeys the semantics defined by MS-DOS instead of Unix. +DOS file systems are case insensitive, file specifications may begin +with a drive letter, and both forward slash and backslash (@samp{/} +and @samp{\}) are directory separators. @item DIR_SEPARATOR @itemx DIR_SEPARATOR_2 If defined, these macros expand to character constants specifying -separators for directory names within a file specification. They are -used somewhat inconsistently throughout the compiler. If your system -behaves like Unix (only forward slash separates pathnames), define -neither of them. If your system behaves like DOS (both forward and -backward slash can be used), define @code{DIR_SEPARATOR} to @samp{/} -and @code{DIR_SEPARATOR_2} to @samp{\}. +separators for directory names within a file specification. +@file{system.h} will automatically give them appropriate values on +Unix and MS-DOS file systems. If your file system is neither of +these, define one or both appropriately in @file{xm-@var{machine}.h}. + +However, operating systems like VMS, where constructing a pathname is +more complicated than just stringing together directory names +separated by a special character, should not define either of these +macros. + +@item PATH_SEPARATOR +If defined, this macro should expand to a character constant +specifying the separator for elements of search paths. The default +value is a colon (@samp{:}). DOS-based systems usually, but not +always, use semicolon (@samp{;}). + +@item VMS +Define this macro if the host system is VMS@. @item HOST_OBJECT_SUFFIX Define this macro to be a C string representing the suffix for object @@ -86,14 +133,6 @@ you do not define this macro, GCC will use @samp{/dev/null} as the bit bucket. If the host does not support a bit bucket, define this macro to an invalid filename. -@item COLLECT2_HOST_INITIALIZATION -If defined, a C statement (sans semicolon) that performs host-dependent -initialization when @code{collect2} is being initialized. - -@item GCC_DRIVER_HOST_INITIALIZATION -If defined, a C statement (sans semicolon) that performs host-dependent -initialization when a compilation driver is being initialized. - @item UPDATE_PATH_HOST_CANONICALIZE (@var{path}) If defined, a C statement (sans semicolon) that performs host-dependent canonicalization when a path used in a compilation driver or @@ -112,6 +151,46 @@ unique to each dump file kind, e.g. @samp{rtl}. If you do not define this macro, GCC will use @samp{.%02d.}. You should define this macro if using the default will create an invalid file name. +@end ftable + +@node Host Misc +@section Host Misc +@cindex configuration file +@cindex @file{xm-@var{machine}.h} + +@ftable @code +@item FATAL_EXIT_CODE +A C expression for the status code to be returned when the compiler +exits after serious errors. The default is the system-provided macro +@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that +macro. Define this macro only if these defaults are incorrect. + +@item SUCCESS_EXIT_CODE +A C expression for the status code to be returned when the compiler +exits without serious errors. (Warnings are not serious errors.) The +default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if +the system doesn't define that macro. Define this macro only if these +defaults are incorrect. + +@item USE_C_ALLOCA +Define this macro if GCC should use the C implementation of @code{alloca} +provided by @file{libiberty.a}. This only affects how some parts of the +compiler itself allocate memory. It does not change code generation. + +When GCC is built with a compiler other than itself, the C @code{alloca} +is always used. This is because most other implementations have serious +bugs. You should define this macro only on a system where no +stack-based @code{alloca} can possibly work. For instance, if a system +has a small limit on the size of the stack, GCC's builtin @code{alloca} +will not work reliably. + +@item COLLECT2_HOST_INITIALIZATION +If defined, a C statement (sans semicolon) that performs host-dependent +initialization when @code{collect2} is being initialized. + +@item GCC_DRIVER_HOST_INITIALIZATION +If defined, a C statement (sans semicolon) that performs host-dependent +initialization when a compilation driver is being initialized. @item SMALL_ARG_MAX Define this macro if the host system has a small limit on the total @@ -123,8 +202,3 @@ In addition, if @command{configure} generates an incorrect definition of any of the macros in @file{auto-host.h}, you can override that definition in a host configuration header. If you need to do this, first see if it is possible to fix @command{configure}. - -If you need to define only a few of these macros, and they have simple -definitions, consider using the @code{xm_defines} variable in your -@file{config.gcc} entry instead of creating a host configuration header. -@xref{System Config}. |
