feat: add BinaryenExpressionAllocateAndWriteText

src/binaryen-c.cpp

@@ -2077,6 +2077,20 @@ BinaryenExpressionRef BinaryenExpressionCopy(BinaryenExpressionRef expr,
                                              BinaryenModuleRef module) {
   return ExpressionManipulator::copy(expr, *(Module*)module);
 }
+char* BinaryenExpressionAllocateAndWriteText(BinaryenExpressionRef expr) {
+  std::ostringstream os;
+  bool colors = Colors::isEnabled();
+
+  Colors::setEnabled(false); // do not use colors for writing
+  os << *(Expression*)expr;
+  Colors::setEnabled(colors); // restore colors state
+
+  auto str = os.str();
+  const size_t len = str.length() + 1;
+  char* output = (char*)malloc(len);
+  std::copy_n(str.c_str(), len, output);
+  return output;
+}
 
 // Specific expression utility
 

src/binaryen-c.h

@@ -1218,6 +1218,11 @@ BINARYEN_API void BinaryenExpressionFinalize(BinaryenExpressionRef expr);
 // Makes a deep copy of the given expression.
 BINARYEN_API BinaryenExpressionRef
 BinaryenExpressionCopy(BinaryenExpressionRef expr, BinaryenModuleRef module);
+// Serialize an expression in s-expression form. Implicitly allocates the
+// returned char* with malloc(), and expects the user to free() them manually
+// once not needed anymore.
+BINARYEN_API char*
+BinaryenExpressionAllocateAndWriteText(BinaryenExpressionRef expr);
 
 // Block
 

src/js/binaryen.js-post.js

@@ -3308,12 +3308,10 @@ Module['emitText'] = function(expr) {
   if (typeof expr === 'object') {
     return expr.emitText();
   }
-  const old = out;
-  let ret = '';
-  out = x => { ret += x + '\n' };
-  Module['_BinaryenExpressionPrint'](expr);
-  out = old;
-  return ret;
+  const textPtr = BinaryenObj["_BinaryenExpressionAllocateAndWriteText"](expr);
+  const text = UTF8ToString(textPtr);
+  if (textPtr) _free(textPtr);
+  return text;
 };
 
 // Calls a function, wrapping it in error handling code so that if it hits a