Add libgif port (#13139)

This is useful in building the JPEG XL reference software, for example.

Author: saschanaz

embuilder.py

@@ -57,6 +57,7 @@
     'bzip2',
     'cocos2d',
     'freetype',
+    'giflib',
     'harfbuzz',
     'icu',
     'libjpeg',
@@ -193,6 +194,8 @@ def main():
       build_port('vorbis', 'libvorbis.a')
     elif what == 'ogg':
       build_port('ogg', 'libogg.a')
+    elif what == 'giflib':
+      build_port('giflib', 'libgif.a')
     elif what == 'libjpeg':
       build_port('libjpeg', 'libjpeg.a')
     elif what == 'libpng':

src/settings.js

@@ -913,7 +913,7 @@ var STRICT = 0;
 // include `_main`.
 var IGNORE_MISSING_MAIN = 1;
 
-// Automatically attempt to add archive indexes at link time to archives that 
+// Automatically attempt to add archive indexes at link time to archives that
 // don't already have them.  This can happen when GNU ar or GNU ranlib is used
 // rather than `llvm-ar` or `emar` since the former don't understand the wasm
 // object format.
@@ -971,7 +971,7 @@ var DETERMINISTIC = 0;
 // (If WASM_ASYNC_COMPILATION is off, that is, if compilation is
 // *synchronous*, then it would not make sense to return a Promise, and instead
 // the Module object itself is returned, which is ready to be used.)
-// 
+//
 // The default name of the function is `Module`, but can be changed using the
 // `EXPORT_NAME` option. We recommend renaming it to a more typical name for a
 // factory function, e.g. `createModule`.
@@ -980,14 +980,14 @@ var DETERMINISTIC = 0;
 // You use the factory function like so:
 //
 //   const module = await EXPORT_NAME();
-//   
+//
 // or:
 //
 //   let module;
 //   EXPORT_NAME().then(instance => {
 //     module = instance;
 //   });
-//   
+//
 //
 // The factory function accepts 1 parameter, an object with default values for
 // the module instance:
@@ -1201,6 +1201,9 @@ var USE_ZLIB = 0;
 // 1 = use bzip2 from emscripten-ports
 var USE_BZIP2 = 0;
 
+// 1 = use giflib from emscripten-ports
+var USE_GIFLIB = 0;
+
 // 1 = use libjpeg from emscripten-ports
 var USE_LIBJPEG = 0;
 

tests/test_other.py

@@ -1499,6 +1499,11 @@ def test_libpng(self):
     output = self.run_js('a.out.js')
     self.assertContained('libpng passes test', output)
 
+  def test_giflib(self):
+    shutil.copyfile(path_from_root('tests', 'third_party', 'giflib', 'treescap.gif'), 'treescap.gif')
+    building.emcc(path_from_root('tests', 'third_party', 'giflib', 'giftext.c'), ['--embed-file', 'treescap.gif', '-s', 'USE_GIFLIB'], output_filename='a.out.js')
+    self.assertContained('GIF file terminated normally', self.run_js('a.out.js', args=['treescap.gif']))
+
   def test_libjpeg(self):
     shutil.copyfile(path_from_root('tests', 'screenshot.jpg'), 'screenshot.jpg')
     building.emcc(path_from_root('tests', 'jpeg_test.c'), ['--embed-file', 'screenshot.jpg', '-s', 'USE_LIBJPEG'], output_filename='a.out.js')