project('has header', 'c', 'cpp')

host_system = host_machine.system()

non_existent_header = 'ouagadougou.h'

# Copy it into the builddir to ensure that it isn't found even if it's there
configure_file(input : non_existent_header,
  output : non_existent_header,
  configuration : configuration_data())

# Test that the fallback to __has_include also works on all compilers
if host_system != 'darwin'
  fallbacks = ['', '\n#undef __has_include']
else
  # On Darwin's clang you can't redefine builtin macros so the above doesn't work
  fallbacks = ['']
endif

foreach fallback : fallbacks
  foreach comp : [meson.get_compiler('c'), meson.get_compiler('cpp')]
    assert(comp.has_header('stdio.h', prefix : fallback), 'Stdio missing.')

    # stdio.h doesn't actually need stdlib.h, but just test that setting the
    # prefix does not result in an error.
    assert(comp.has_header('stdio.h', prefix : '#include <stdlib.h>' + fallback),
           'Stdio missing.')

    # XInput.h should not require type definitions from windows.h, but it does
    # require macro definitions. Specifically, it requires an arch setting for
    # VS2015 at least.
    # We only do this check on MSVC because MinGW often defines its own wrappers
    # that pre-include windows.h
    if comp.get_id() == 'msvc'
      assert(comp.has_header('XInput.h', prefix : '#include <windows.h>' + fallback),
             'XInput.h should not be missing on Windows')
      assert(comp.has_header('XInput.h', prefix : '#define _X86_' + fallback),
             'XInput.h should not need windows.h')
    endif

    # Test that the following GCC bug doesn't happen:
    # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80005
    # https://github.com/mesonbuild/meson/issues/1458
    if host_system == 'linux'
      assert(comp.has_header('linux/if.h', prefix : fallback),
             'Could not find <linux/if.h>')
    endif

    # This header exists in the source and the builddir, but we still must not
    # find it since we are looking in the system directories.
    assert(not comp.has_header(non_existent_header, prefix : fallback),
           'Found non-existent header.')
  endforeach
endforeach