@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, @c 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. @c This is part of the GCC manual. @c For copying conditions, see the file gccint.texi. @node Host Config @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}, int @var{fd}) This host hook returns the address of some space that is likely to be free in some subsequent invocation of the compiler. We intend to load the PCH data at this address such that the data need not be relocated. The area should be able to hold @var{size} bytes. If the host uses @code{mmap}, @var{fd} is an open file descriptor that can be used for probing. @end deftypefn @deftypefn {Host Hook} int HOST_HOOKS_GT_PCH_USE_ADDRESS (void * @var{address}, size_t @var{size}, int @var{fd}, size_t @var{offset}) This host hook is called when a PCH file is about to be loaded. We want to load @var{size} bytes from @var{fd} at @var{offset} into memory at @var{address}. The given address will be the result of a previous invocation of @code{HOST_HOOKS_GT_PCH_GET_ADDRESS}. Return @minus{}1 if we couldn't allocate @var{size} bytes at @var{address}. Return 0 if the memory is allocated but the data is not loaded. Return 1 if the hook has performed everything. If the implementation uses reserved address space, free any reserved space beyond @var{size}, regardless of the return value. 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 @minus{}1. 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 @deftypefn {Host Hook} size_t HOST_HOOKS_GT_PCH_ALLOC_GRANULARITY (void); This host hook returns the alignment required for allocating virtual memory. Usually this is the same as getpagesize, but on some hosts the alignment for reserving memory differs from the pagesize for committing memory. @end deftypefn @node Filesystem @section Host Filesystem @cindex configuration file @cindex @file{xm-@var{machine}.h} 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 HAVE_DOS_BASED_FILE_SYSTEM 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. @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 files on your host machine. If you do not define this macro, GCC will use @samp{.o} as the suffix for object files. @item HOST_EXECUTABLE_SUFFIX Define this macro to be a C string representing the suffix for executable files on your host machine. If you do not define this macro, GCC will use the null string as the suffix for executable files. @item HOST_BIT_BUCKET A pathname defined by the host operating system, which can be opened as a file and written to, but all the information written is discarded. This is commonly known as a @dfn{bit bucket} or @dfn{null device}. If 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 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 preprocessor is canonicalized. @var{path} is a malloc-ed path to be canonicalized. If the C statement does canonicalize @var{path} into a different buffer, the old path should be freed and the new buffer should have been allocated with malloc. @item DUMPFILE_FORMAT Define this macro to be a C string representing the format to use for constructing the index part of debugging dump file names. The resultant string must fit in fifteen bytes. The full filename will be the concatenation of: the prefix of the assembler file name, the string resulting from applying this format to an index number, and a string 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. @item DELETE_IF_ORDINARY Define this macro to be a C statement (sans semicolon) that performs host-dependent removal of ordinary temp files in the compilation driver. If you do not define this macro, GCC will use the default version. You should define this macro if the default version does not reliably remove the temp file as, for example, on VMS which allows multiple versions of a file. @item HOST_LACKS_INODE_NUMBERS Define this macro if the host filesystem does not report meaningful inode numbers in struct stat. @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 HOST_LONG_LONG_FORMAT If defined, the string used to indicate an argument of type @code{long long} to functions like @code{printf}. The default value is @code{"ll"}. @end ftable 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}.