Bug 1507032 - Work around bug in wayland (< 1.12) headers. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D11837

--HG--
extra : moz-landing-system : lando

config/make-system-wrappers.py

@@ -7,16 +7,32 @@ from mozbuild.util import FileAvoidWrite
 
 header_template = '''#pragma GCC system_header
 #pragma GCC visibility push(default)
-#include_next <%(header)s>
+{includes}
 #pragma GCC visibility pop
 '''
 
+include_next_template = '#include_next <{header}>'
+
 
 # The 'unused' arg is the output file from the file_generate action. We actually
 # generate all the files in header_list
 def gen_wrappers(unused, outdir, *header_list):
     for header in header_list:
         with FileAvoidWrite(os.path.join(outdir, header)) as f:
-            f.write(header_template % {
-                'header': header,
-            })
+            includes = include_next_template.format(header=header)
+            if header == 'wayland-util.h':
+                # wayland-util.h in Wayland < 1.12 includes math.h inside an
+                # extern "C" block, which breaks including the header from C++.
+                # This was fixed in Wayland 1.12, but for versions earlier than
+                # that, we work around that by force-including math.h first.
+                includes = '#include <math.h>\n' + includes
+            elif header == 'wayland-client.h':
+                # The system wayland-client.h uses quote includes for
+                # wayland-util.h, which means wayland-util.h is picked from the
+                # directory containing wayland-client.h first, and there's no
+                # way around that with -I, -isystem, or other flags. So, we
+                # force to include it from our wrapper, before including the
+                # system header, so that our wayland-util.h wrapper is picked
+                # first.
+                includes = '#include "wayland-util.h"\n' + includes
+            f.write(header_template.format(includes=includes))

config/system-headers.mozbuild

@@ -1348,6 +1348,7 @@ if CONFIG['MOZ_WAYLAND']:
         'xkbcommon/xkbcommon.h',
         'wayland-client.h',
         'wayland-egl.h',
+        'wayland-util.h',
     ]
 
 if CONFIG['MOZ_LIB_SECRET']: