add a --symbolmap option to wasm-as, which emits a side file with the name mapping (similar to Names section, but external)

3 files changed, 21 insertions, 0 deletions

diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 95e6c9371..067c0f28d 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -29,6 +29,7 @@ using namespace wasm;
 
 int main(int argc, const char *argv[]) {
   bool debugInfo = false;
+  std::string symbolMap;
   Options options("wasm-as", "Assemble a .wast (WebAssembly text format) into a .wasm (WebAssembly binary format)");
   options.extra["validate"] = "wasm";
   options
@@ -50,6 +51,9 @@ int main(int argc, const char *argv[]) {
       .add("--debuginfo", "-g", "Emit names section and debug info",
            Options::Arguments::Zero,
            [&](Options *o, const std::string &arguments) { debugInfo = true; })
+      .add("--symbolmap", "-s", "Emit a symbol map (indexes => names)",
+           Options::Arguments::One,
+           [&](Options *o, const std::string &argument) { symbolMap = argument; })
       .add_positional("INFILE", Options::Arguments::One,
                       [](Options *o, const std::string &argument) {
                         o->extra["infile"] = argument;
@@ -83,6 +87,7 @@ int main(int argc, const char *argv[]) {
   BufferWithRandomAccess buffer(options.debug);
   WasmBinaryWriter writer(&wasm, buffer, options.debug);
   writer.setDebugInfo(debugInfo);
+  if (symbolMap.size() > 0) writer.setSymbolMap(symbolMap);
   writer.write();
 
   if (options.debug) std::cerr << "writing to output..." << std::endl;
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index efff5a77b..6ec55f757 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -527,6 +527,7 @@ class WasmBinaryWriter : public Visitor<WasmBinaryWriter, void> {
   BufferWithRandomAccess& o;
   bool debug;
   bool debugInfo = true;
+  std::string symbolMap;
 
   MixedArena allocator;
 
@@ -537,6 +538,7 @@ public:
   }
 
   void setDebugInfo(bool set) { debugInfo = set; }
+  void setSymbolMap(std::string set) { symbolMap = set; }
 
   void write();
   void writeHeader();
@@ -569,6 +571,7 @@ public:
   void writeFunctionTableDeclaration();
   void writeTableElements();
   void writeNames();
+  void writeSymbolMap();
 
   // helpers
   void writeInlineString(const char* name);
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index d2a648294..2a81bdc46 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -43,6 +43,7 @@ void WasmBinaryWriter::write() {
   writeFunctions();
   writeDataSegments();
   if (debugInfo) writeNames();
+  if (symbolMap.size() > 0) writeSymbolMap();
 
   finishUp();
 }
@@ -380,6 +381,18 @@ void WasmBinaryWriter::writeNames() {
   finishSection(start);
 }
 
+void WasmBinaryWriter::writeSymbolMap() {
+  std::ofstream file(symbolMap);
+  for (auto& import : wasm->imports) {
+    if (import->kind == ExternalKind::Function) {
+      file << getFunctionIndex(import->name) << ":" << import->name.str << std::endl;
+    }
+  }
+  for (auto& func : wasm->functions) {
+    file << getFunctionIndex(func->name) << ":" << func->name.str << std::endl;
+  }
+  file.close();
+}
 
 void WasmBinaryWriter::writeInlineString(const char* name) {
   int32_t size = strlen(name);