8. Host Definition

With the advent of Autoconf, it's rarely necessary to have host definition machinery anymore. The following information is provided, mainly, as an historical reference.

8.1 Adding a New Host

GDB's host configuration support normally happens via Autoconf. New host-specific definitions should not be needed. Older hosts GDB still use the host-specific definitions and files listed below, but these mostly exist for historical reasons, and will eventually disappear.

`gdb/config/arch/xyz.mh'

This file once contained both host and native configuration information (see section 11. Native Debugging) for the machine xyz. The host configuration information is now handed by Autoconf.

Host configuration information included a definition of XM_FILE=xm-xyz.h and possibly definitions for CC, SYSV_DEFINE, XM_CFLAGS, XM_ADD_FILES, XM_CLIBS, XM_CDEPS, etc.; see `Makefile.in'.

New host only configurations do not need this file.

`gdb/config/arch/xm-xyz.h'

This file once contained definitions and includes required when hosting gdb on machine xyz. Those definitions and includes are now handled by Autoconf.

New host and native configurations do not need this file.

Maintainer's note: Some hosts continue to use the `xm-xyz.h' file to define the macros HOST_FLOAT_FORMAT, HOST_DOUBLE_FORMAT and HOST_LONG_DOUBLE_FORMAT. That code also needs to be replaced with either an Autoconf or run-time test.

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 `xm-xyz.h' file. If these routines work for the xyz host, you can just include the generic file's name (with `.o', not `.c') in 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 xyz-xdep.c, and put xyz-xdep.o into XDEPFILES.

`ser-unix.c'

This contains serial line support for Unix systems. This is always included, via the makefile variable SER_HARDWIRE; override this variable in the `.mh' file to avoid it.

`ser-go32.c'

This contains serial line support for 32-bit programs running under DOS, using the DJGPP (a.k.a. GO32) execution environment.

`ser-tcp.c'

This contains generic TCP support using sockets.

8.2 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 (or if the meaning is not documented here, then one of the source files where they are used is indicated) are:

GDBINIT_FILENAME

The default name of GDB's initialization file (normally `.gdbinit').

NO_STD_REGS

This macro is deprecated.

NO_SYS_FILE

Define this if your system does not have a <sys/file.h>.

SIGWINCH_HANDLER

If your host defines SIGWINCH, you can define this to be the name of a function to be called if SIGWINCH is received.

SIGWINCH_HANDLER_BODY

Define this to expand into code that will define the function named by the expansion of SIGWINCH_HANDLER.

ALIGN_STACK_ON_STARTUP

Define this if your system is of a sort that will crash in tgetent if the stack happens not to be longword-aligned when main is called. This is a rare situation, but is known to occur on several different types of systems.

CRLF_SOURCE_FILES

Define this if host files use \r\n rather than \n as a line terminator. This will cause source file listings to omit \r characters when printing and it will allow \r\n line endings of files which are "sourced" by gdb. It must be possible to open files in binary mode using O_BINARY or, for fopen, "rb".

DEFAULT_PROMPT

The default value of the prompt string (normally "(gdb) ").

DEV_TTY

The name of the generic TTY device, defaults to "/dev/tty".

FCLOSE_PROVIDED

Define this if the system declares fclose in the headers included in defs.h. This isn't needed unless your compiler is unusually anal.

FOPEN_RB

Define this if binary files are opened the same way as text files.

GETENV_PROVIDED

Define this if the system declares getenv in its headers included in defs.h. This isn't needed unless your compiler is unusually anal.

HAVE_MMAP

In some cases, use the system call mmap for reading symbol tables. For some machines this allows for sharing and quick updates.

HAVE_TERMIO

Define this if the host system has termio.h.

INT_MAX

INT_MIN

LONG_MAX

UINT_MAX

ULONG_MAX

Values for host-side constants.

ISATTY

Substitute for isatty, if not available.

LONGEST

This is the longest integer type available on the host. If not defined, it will default to long long or long, depending on CC_HAS_LONG_LONG.

CC_HAS_LONG_LONG

Define this if the host C compiler supports long long. This is set by the configure script.

PRINTF_HAS_LONG_LONG

Define this if the host can handle printing of long long integers via the printf format conversion specifier ll. This is set by the configure script.

HAVE_LONG_DOUBLE

Define this if the host C compiler supports long double. This is set by the configure script.

PRINTF_HAS_LONG_DOUBLE

Define this if the host can handle printing of long double float-point numbers via the printf format conversion specifier Lg. This is set by the configure script.

SCANF_HAS_LONG_DOUBLE

Define this if the host can handle the parsing of long double float-point numbers via the scanf format conversion specifier Lg. This is set by the configure script.

LSEEK_NOT_LINEAR

Define this if lseek (n) does not necessarily move to byte number n in the file. This is only used when reading source files. It is normally faster to define CRLF_SOURCE_FILES when possible.

L_SET

This macro is used as the argument to lseek (or, most commonly, bfd_seek). FIXME, should be replaced by SEEK_SET instead, which is the POSIX equivalent.

MMAP_BASE_ADDRESS

When using HAVE_MMAP, the first mapping should go at this address.

MMAP_INCREMENT

when using HAVE_MMAP, this is the increment between mappings.

NORETURN

If defined, this should be one or more tokens, such as volatile, that can be used in both the declaration and definition of functions to indicate that they never return. The default is already set correctly if compiling with GCC. This will almost never need to be defined.

ATTR_NORETURN

If defined, this should be one or more tokens, such as __attribute__ ((noreturn)), that can be used in the declarations of functions to indicate that they never return. The default is already set correctly if compiling with GCC. This will almost never need to be defined.

USE_GENERIC_DUMMY_FRAMES

Define this to 1 if the target is using the generic inferior function call code. See blockframe.c for more information.

USE_MMALLOC

GDB will use the mmalloc library for memory allocation for symbol reading if this symbol is defined. Be careful defining it since there are systems on which mmalloc does not work for some reason. One example is the DECstation, where its RPC library can't cope with our redefinition of malloc to call mmalloc. When defining USE_MMALLOC, you will also have to set MMALLOC in the Makefile, to point to the mmalloc library. This define is set when you configure with `--with-mmalloc'.

NO_MMCHECK

Define this if you are using mmalloc, but don't want the overhead of checking the heap with mmcheck. Note that on some systems, the C runtime makes calls to malloc prior to calling main, and if free is ever called with these pointers after calling mmcheck to enable checking, a memory corruption abort is certain to occur. These systems can still use mmalloc, but must define NO_MMCHECK.

MMCHECK_FORCE

Define this to 1 if the C runtime allocates memory prior to mmcheck being called, but that memory is never freed so we don't have to worry about it triggering a memory corruption abort. The default is 0, which means that mmcheck will only install the heap checking functions if there has not yet been any memory allocation calls, and if it fails to install the functions, GDB will issue a warning. This is currently defined if you configure using `--with-mmalloc'.

NO_SIGINTERRUPT

Define this to indicate that siginterrupt is not available.

SEEK_CUR

SEEK_SET

Define these to appropriate value for the system lseek, if not already defined.

STOP_SIGNAL

This is the signal for stopping GDB. Defaults to SIGTSTP. (Only redefined for the Convex.)

USE_O_NOCTTY

Define this if the interior's tty should be opened with the O_NOCTTY flag. (FIXME: This should be a native-only flag, but `inflow.c' is always linked in.)

USG

Means that System V (prior to SVR4) include files are in use. (FIXME: This symbol is abused in `infrun.c', `regex.c', `remote-nindy.c', and `utils.c' for other things, at the moment.)

lint

Define this to help placate lint in some situations.

volatile

Define this to override the defaults of __volatile__ or /**/.