Fix __cxa_find_matching_catch's memory leak (emscripten-core#8947)

aheejin · web-flow · commit fe7d36f7b425 · 2019-07-09T16:31:52.000-07:00
`__cxa_find_matching_catch` allocated a buffer of size 4 using `malloc` only when it was first called and reused it through the entire program run. And this malloc'ed memory wasn't freed. Because this is only allocated once, I changed it to a static allocation using `makeStaticAlloc`. Fixes emscripten-core#8919.
diff --git a/src/library_exceptions.js b/src/library_exceptions.js
@@ -279,12 +279,16 @@ var LibraryExceptions = {
 
     var pointer = {{{ exportedAsmFunc('___cxa_is_pointer_type') }}}(throwntype);
     // can_catch receives a **, add indirection
-    if (!___cxa_find_matching_catch.buffer) ___cxa_find_matching_catch.buffer = _malloc(4);
 #if EXCEPTION_DEBUG
     out("can_catch on " + [thrown]);
 #endif
-    {{{ makeSetValue('___cxa_find_matching_catch.buffer', '0', 'thrown', '*') }}};
-    thrown = ___cxa_find_matching_catch.buffer;
+#if DISABLE_EXCEPTION_CATCHING == 1
+    var buffer = 0;
+#else
+    var buffer = {{{ makeStaticAlloc(4) }}};
+#endif
+    {{{ makeSetValue('buffer', '0', 'thrown', '*') }}};
+    thrown = buffer;
     // The different catch blocks are denoted by different types.
     // Due to inheritance, those types may not precisely match the
     // type of the thrown object. Find one which matches, and
