#### Cross-compiling the GLib package

## 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 Meson documentation.

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 meson via a ‘cross file’.

As an example of using a cross file, to cross compile for the ‘MingW32’ Win64 runtime environment on a Linux system, create a file `cross_file.txt` with the following contents:

    [host_machine]
    system = 'windows'
    cpu_family = 'x86_64'
    cpu = 'x86_64'
    endian = 'little'

    [properties]
    c_args = []
    c_link_args = []

    [binaries]
    c = 'x86_64-w64-mingw32-gcc'
    cpp = 'x86_64-w64-mingw32-g++'
    ar = 'x86_64-w64-mingw32-ar'
    ld = 'x86_64-w64-mingw32-ld'
    objcopy = 'x86_64-w64-mingw32-objcopy'
    strip = 'x86_64-w64-mingw32-strip'
    pkgconfig = 'x86_64-w64-mingw32-pkg-config'
    windres = 'x86_64-w64-mingw32-windres'

Then execute the following commands:

    meson setup --cross-file cross_file.txt builddir

The complete list of cross properties follows. Most of these won’t need to be set in most cases.

## Cross properties

`have_[function]`

  When meson checks if a function is supported, the test can be overridden by setting the `have_function` property to `true` or `false`. For example:

  Checking for function “fsync” : YES

can be overridden by setting

    have_fsync = false

`growing_stack=[true/false]`
  Whether the stack grows up or down. Most places will want `false`. A few architectures, such as PA-RISC need `true`.
`have_strlcpy=[true/false]`
  Whether you have `strlcpy()` that matches OpenBSD. Defaults to `false`, which is safe, since GLib uses a built-in version in that case.
`va_val_copy=[true/false]`
  Whether `va_list` can be copied as a pointer. If set to `false`, 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 `true` which is slightly more common than `false`.
`have_c99_vsnprintf=[true/false]`
  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 `false`.
`have_c99_snprintf=[true/false]`
  Whether you have a `snprintf()` 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 `false`.