EMSCRIPTEN_COMMENT for source comments

3 files changed, 31 insertions, 3 deletions

diff --git a/src/jsifier.js b/src/jsifier.js
index cd59d43c..9c34ddf1 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -838,6 +838,12 @@ function JSify(data, functionsOnly, givenFunctions, givenGlobalVariables) {
       return makeSetValue(params[0].ident, 0, data, 'void*');
     } else if (ident == '_llvm_va_end') {
       return ';';
+    } else if (ident == '_EMSCRIPTEN_COMMENT') {
+      var param = finalizeParam(params[0]);
+      if (param.indexOf('CHECK_OVERFLOW') >= 0) {
+        param = param.split('(')[1].split(',')[0];
+      }
+      return '// ' + GLOBAL_VARIABLES[param].value.text.replace('\\00', '') + '   ';
     }
 
     var func = Functions.currFunctions[ident] || Functions.currExternalFunctions[ident];
diff --git a/system/include/emscripten.h b/system/include/emscripten.h
index 5f3689c9..4d321b2c 100644
--- a/system/include/emscripten.h
+++ b/system/include/emscripten.h
@@ -7,7 +7,23 @@
  * http://emscripten.org
  */
 
-// Interface to the underlying JS engine. This function will
-// eval() the given script.
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Interface to the underlying JS engine. This function will
+ * eval() the given script.
+ */
 extern void emscripten_run_script(const char *script);
 
+/*
+ * This macro-looking function will cause Emscripten to
+ * generate a comment in the generated code.
+ */
+extern void EMSCRIPTEN_COMMENT(const char *text);
+
+#ifdef __cplusplus
+}
+#endif
+
diff --git a/tests/runner.py b/tests/runner.py
index 3f124df7..bf71cf2c 100644
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -1430,11 +1430,17 @@ if 'benchmark' not in str(sys.argv):
           #include "emscripten.h"
 
           int main() {
+            EMSCRIPTEN_COMMENT("hello from the source");
             emscripten_run_script("print('hello world' + '!')");
             return 0;
           }
           '''
-        self.do_test(src, 'hello world!')
+
+        def check(filename):
+          src = open(filename, 'r').read()
+          assert '// hello from the source' in src
+
+        self.do_test(src, 'hello world!', post_build=check)
 
     def test_ssr(self): # struct self-ref
         src = '''