3 files changed, 58 insertions, 22 deletions

diff --git a/src/binaryen-c.cpp b/src/binaryen-c.cpp
index c2ba7fa6b..f3f21bc15 100644
--- a/src/binaryen-c.cpp
+++ b/src/binaryen-c.cpp
@@ -2063,7 +2063,7 @@ void BinaryenSetDebugInfo(int on) {
     std::cout << "  BinaryenSetDebugInfo(" << on << ");\n";
   }
 
-  globalPassOptions.debugInfo = bool(on);
+  globalPassOptions.debugInfo = on != 0;
 }
 
 void BinaryenModuleRunPasses(BinaryenModuleRef module, const char **passes, BinaryenIndex numPasses) {
@@ -2139,6 +2139,33 @@ BinaryenBufferSizes BinaryenModuleWriteWithSourceMap(BinaryenModuleRef module, c
   return writeModule((Module*)module, output, outputSize, url, sourceMap, sourceMapSize);
 }
 
+BinaryenModuleAllocateAndWriteResult BinaryenModuleAllocateAndWrite(BinaryenModuleRef module, const char* sourceMapUrl) {
+  if (tracing) {
+    std::cout << " // BinaryenModuleAllocateAndWrite(the_module, ";
+    traceNameOrNULL(sourceMapUrl);
+    std::cout << ");\n";
+  }
+
+  Module* wasm = (Module*)module;
+  BufferWithRandomAccess buffer(false);
+  WasmBinaryWriter writer(wasm, buffer, false);
+  writer.setNamesSection(globalPassOptions.debugInfo);
+  std::ostringstream os;
+  if (sourceMapUrl) {
+    writer.setSourceMap(&os, sourceMapUrl);
+  }
+  writer.write();
+  void* binary = malloc(buffer.size());
+  std::copy_n(buffer.begin(), buffer.size(), static_cast<char*>(binary));
+  char* sourceMap = nullptr;
+  if (sourceMapUrl) {
+    auto str = os.str();
+    sourceMap = (char*)malloc(str.length() + 1);
+    std::copy_n(str.c_str(), str.length() + 1, sourceMap);
+  }
+  return { binary, buffer.size(), sourceMap };
+}
+
 BinaryenModuleRef BinaryenModuleRead(char* input, size_t inputSize) {
   if (tracing) {
     std::cout << "  // BinaryenModuleRead\n";
diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index 9033a6950..87c44db60 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -707,6 +707,20 @@ typedef struct BinaryenBufferSizes {
 // @returns how many bytes were written. This will be less than or equal to outputSize
 BinaryenBufferSizes BinaryenModuleWriteWithSourceMap(BinaryenModuleRef module, const char* url, char* output, size_t outputSize, char* sourceMap, size_t sourceMapSize);
 
+// Result structure of BinaryenModuleAllocateAndWrite. Contained buffers have been allocated
+// using malloc() and the user is expected to free() them manually once not needed anymore.
+typedef struct BinaryenModuleAllocateAndWriteResult {
+  void* binary;
+  size_t binaryBytes;
+  char* sourceMap;
+} BinaryenModuleAllocateAndWriteResult;
+
+// Serializes a module into binary form, optionally including its source map if
+// sourceMapUrl has been specified. Uses the currently set global debugInfo option.
+// Differs from BinaryenModuleWrite in that it implicitly allocates appropriate buffers
+// using malloc(), and expects the user to free() them manually once not needed anymore.
+BinaryenModuleAllocateAndWriteResult BinaryenModuleAllocateAndWrite(BinaryenModuleRef module, const char* sourceMapUrl);
+
 // Deserialize a module from binary form.
 BinaryenModuleRef BinaryenModuleRead(char* input, size_t inputSize);
 
diff --git a/src/js/binaryen.js-post.js b/src/js/binaryen.js-post.js
index 5f1ef84fb..e9b4039f7 100644
--- a/src/js/binaryen.js-post.js
+++ b/src/js/binaryen.js-post.js
@@ -1160,7 +1160,7 @@ Module['Module'] = function(module) {
     return Module['_BinaryenModuleOptimize'](module);
   };
   this['optimizeFunction'] = function(func) {
-    if (typeof func === "string") func = this['getFunction'](func);
+    if (typeof func === 'string') func = this['getFunction'](func);
     return Module['_BinaryenFunctionOptimize'](func, module);
   };
   this['runPasses'] = function(passes) {
@@ -1171,7 +1171,7 @@ Module['Module'] = function(module) {
     });
   };
   this['runPassesOnFunction'] = function(func, passes) {
-    if (typeof func === "string") func = this['getFunction'](func);
+    if (typeof func === 'string') func = this['getFunction'](func);
     return preserveStack(function() {
       return Module['_BinaryenFunctionRunPasses'](func, module, i32sToStack(
         passes.map(strToStack)
@@ -1184,27 +1184,22 @@ Module['Module'] = function(module) {
   this['dispose'] = function() {
     Module['_BinaryenModuleDispose'](module);
   };
-  var MAX = 1024*1024; // TODO: fix this hard-wired limit
-  var outputBuffer = null;
-  var sourceMapBuffer = null;
   this['emitBinary'] = function(sourceMapUrl) {
-    if (!outputBuffer) outputBuffer = _malloc(MAX);
-    var bytes = Module['_BinaryenModuleWrite'](module, outputBuffer, MAX);
-    assert(bytes < MAX, 'FIXME: hardcoded limit on module size'); // we should not use the whole buffer
-    return new Uint8Array(HEAPU8.subarray(outputBuffer, outputBuffer + bytes));
-  };
-  this['emitBinaryWithSourceMap'] = function(sourceMapUrl) {
-    if (!outputBuffer) outputBuffer = _malloc(MAX);
-    if (!sourceMapBuffer) sourceMapBuffer = _malloc(MAX);
     return preserveStack(function() {
-      Module['_BinaryenModuleWriteWithSourceMap'](temp, module, strToStack(sourceMapUrl), outputBuffer, MAX, sourceMapBuffer, MAX);
-      var outputBytes = HEAPU32[temp >>> 2];
-      var sourceMapBytes = HEAPU32[(temp + 1) >>> 2];
-      assert(outputBytes < MAX && sourceMapBytes < MAX, 'FIXME: hardcoded limit on module size'); // see above
-      return {
-        'binary': new Uint8Array(HEAPU8.subarray(outputBuffer, outputBuffer + outputBytes)),
-        'sourceMap': Pointer_stringify(sourceMapBuffer)
-      };
+      Module['_BinaryenModuleAllocateAndWrite'](temp, module, strToStack(sourceMapUrl));
+      var binaryPtr    = HEAPU32[ temp >>> 2     ];
+      var binaryBytes  = HEAPU32[(temp >>> 2) + 1];
+      var sourceMapPtr = HEAPU32[(temp >>> 2) + 2];
+      try {
+        var buffer = new Uint8Array(binaryBytes);
+        buffer.set(HEAPU8.subarray(binaryPtr, binaryPtr + binaryBytes));
+        return typeof sourceMapUrl === 'undefined'
+          ? buffer
+          : { 'binary': buffer, 'sourceMap': Pointer_stringify(sourceMapPtr) };
+      } finally {
+        _free(binaryPtr);
+        if (sourceMapPtr) _free(sourceMapPtr);
+      }
     });
   };
   this['interpret'] = function() {