Building the Library for a different architecture

Cross-compilation is the process of compiling a program or library on a different architecture or operating system then it will be run upon. GLib is slightly more difficult to cross-compile than many packages because much of GLib is about hiding differences between different systems.

These notes cover things specific to cross-compiling GLib; for general information about cross-compilation, see the autoconf info pages.

GLib tries to detect as much information as possible about the target system by compiling and linking programs without actually running anything; however, some information GLib needs is not available this way. This information needs to be provided to the configure script via a "cache file" or by setting the cache variables in your environment.

As an example of using a cache file, to cross compile for the "MingW32" Win32 runtine environment on a Linux system, create a file 'win32.cache' with the following contents:

 
glib_cv_long_long_format=I64
glib_cv_stack_grows=no
      

Then execute the following commands:

PATH=/path/to/mingw32-compiler/bin:$PATH
chmod a-w win32.cache   # prevent configure from changing it
./configure --cache-file=win32.cache --host=mingw32
      

The complete list of cache file variables follows. Most of these won't need to be set in most cases.

Cache file variables

glib_cv_long_long_format=[ll/q/I64].  Format used by printf() and scanf() for 64 bit integers. "ll" is the C99 standard, and what is used by the 'trio' library that GLib builds if your printf() is insufficiently capable. Doesn't need to be set if you are compiling using trio.

glib_cv_stack_grows=[yes/no].  Whether the stack grows up or down. Most places will want "no", A few architectures, such as PA-RISC need "yes".

glib_cv_working_bcopy=[yes/no].  Whether your bcopy() can handle overlapping copies. Only needs to be set if you don't have memmove(). (Very unlikely)

glib_cv_sane_realloc=[yes/np].  Whether your realloc() conforms to ANSI C and can handle NULL as the first argument. Defaults to "yes" and probably doesn't need to be set.

glib_cv_have_strlcpy=[yes/no].  Whether you have strlcpy() that matches OpenBSD. Defaults to "no", which is safe, since GLib uses a built-in version in that case.

glib_cv_va_val_copy=[yes/no].  Whether va_list can be copied as a pointer. If set to "no", then memcopy() will be used. Only matters if you don't have va_copy() or __va_copy(). (So, doesn't matter for GCC.) Defaults to "yes" which is slightly more common than "no".

glib_cv_rtldglobal_broken=[yes/no].  Whether you have a bug found in OSF/1 v5.0. Defaults to "no".

glib_cv_uscore=[yes/no].  Whether an underscore needs to be prepended to symbols when looking them up via dlsym(). Only needs to be set if your system uses dlopen()/dlsym().

ac_cv_func_posix_getpwuid_r=[yes/no].  Whether you have a getpwuid_r function (in your C library, not your thread library) that conforms to the POSIX spec. (Takes a 'struct passwd **' as the final argument)

ac_cv_func_nonposix_getpwuid_r=[yes/no].  Whether you have some variant of getpwuid_r() that doesn't conform to to the POSIX spec, but GLib might be able to use (or might segfault.) Only needs to be set if ac_cv_func_posix_getpwuid_r is not set. It's safest to set this to "no".

glib_cv_use_pid_surrogate=[yes/no].  Whether to use a setpriority() on the PID of the thread as a method for setting the priority of threads. This only needs to be set when using POSIX threads.

ac_cv_func_printf_unix98=[yes/no].  Whether your printf() family supports Unix98 style %N$ positional parameters. Defaults to "no".

ac_cv_func_vsnprintf_c99=[yes/no].  Whether you have a vsnprintf() with C99 semantics. (C99 semantics means returning the number of bytes that would have been written had the output buffer had enough space.) Defaults to "no".