1 files changed, 28 insertions, 23 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index d7c052a9f..d4fda5915 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -398,8 +398,10 @@ void WasmBinaryWriter::writeFunctions() {
   bool DWARF = Debug::hasDWARFSections(*getModule());
   ModuleUtils::iterDefinedFunctions(*wasm, [&](Function* func) {
     assert(binaryLocationTrackedExpressionsForFunc.empty());
-    size_t sourceMapLocationsSizeAtFunctionStart = sourceMapLocations.size();
     BYN_TRACE("write one at" << o.size() << std::endl);
+    // Do not smear any debug location from the previous function.
+    writeNoDebugLocation();
+    size_t sourceMapLocationsSizeAtFunctionStart = sourceMapLocations.size();
     size_t sizePos = writeU32LEBPlaceholder();
     size_t start = o.size();
     BYN_TRACE("writing" << func->name << std::endl);
@@ -1373,6 +1375,28 @@ void WasmBinaryWriter::writeDebugLocation(const Function::DebugLocation& loc) {
   lastDebugLocation = loc;
 }
 
+void WasmBinaryWriter::writeNoDebugLocation() {
+  // Emit an indication that there is no debug location there (so that
+  // we do not get "smeared" with debug info from anything before or
+  // after us).
+  //
+  // We don't need to write repeated "no debug info" indications, as a
+  // single one is enough to make it clear that the debug information
+  // before us is valid no longer. We also don't need to write one if
+  // there is nothing before us.
+  if (!sourceMapLocations.empty() &&
+      sourceMapLocations.back().second != nullptr) {
+    sourceMapLocations.emplace_back(o.size(), nullptr);
+
+    // Initialize the state of debug info to indicate there is no current
+    // debug info relevant. This sets |lastDebugLocation| to a dummy value,
+    // so that later places with debug info can see that they differ from
+    // it (without this, if we had some debug info, then a nullptr for none,
+    // and then the same debug info, we could get confused).
+    initializeDebugInfo();
+  }
+}
+
 void WasmBinaryWriter::writeDebugLocation(Expression* curr, Function* func) {
   if (sourceMap) {
     auto& debugLocations = func->debugLocations;
@@ -1381,25 +1405,8 @@ void WasmBinaryWriter::writeDebugLocation(Expression* curr, Function* func) {
       // There is debug information here, write it out.
       writeDebugLocation(iter->second);
     } else {
-      // This expression has no debug location. We need to emit an indication
-      // of that (so that we do not get "smeared" with debug info from anything
-      // before or after us).
-      //
-      // We don't need to write repeated "no debug info" indications, as a
-      // single one is enough to make it clear that the debug information before
-      // us is valid no longer. We also don't need to write one if there is
-      // nothing before us.
-      if (!sourceMapLocations.empty() &&
-          sourceMapLocations.back().second != nullptr) {
-        sourceMapLocations.emplace_back(o.size(), nullptr);
-
-        // Initialize the state of debug info to indicate there is no current
-        // debug info relevant. This sets |lastDebugLocation| to a dummy value,
-        // so that later places with debug info can see that they differ from
-        // it (without this, if we had some debug info, then a nullptr for none,
-        // and then the same debug info, we could get confused).
-        initializeDebugInfo();
-      }
+      // This expression has no debug location.
+      writeNoDebugLocation();
     }
   }
   // If this is an instruction in a function, and if the original wasm had
@@ -2687,12 +2694,11 @@ void WasmBinaryReader::readFunctions() {
 
     readVars();
 
-    std::swap(func->prologLocation, debugLocation);
+    func->prologLocation = debugLocation;
     {
       // process the function body
       BYN_TRACE("processing function: " << i << std::endl);
       nextLabel = 0;
-      debugLocation.clear();
       willBeIgnored = false;
       // process body
       assert(breakStack.empty());
@@ -2931,7 +2937,6 @@ void WasmBinaryReader::readNextDebugLocation() {
 
   if (nextDebugPos == 0) {
     // We reached the end of the source map; nothing left to read.
-    debugLocation.clear();
     return;
   }