Exporting/importing debug location information from .wast/.asm.js/.s formats (#1017)

* Extends wasm-as, wasm-dis and s2wasm to consume debug locations.

* Exports source map from asm2wasm

3 files changed, 51 insertions, 4 deletions

diff --git a/src/tools/asm2wasm.cpp b/src/tools/asm2wasm.cpp
index cf0715198..3fa97d981 100644
--- a/src/tools/asm2wasm.cpp
+++ b/src/tools/asm2wasm.cpp
@@ -36,6 +36,8 @@ int main(int argc, const char *argv[]) {
   bool legalizeJavaScriptFFI = true;
   Asm2WasmBuilder::TrapMode trapMode = Asm2WasmBuilder::TrapMode::JS;
   bool wasmOnly = false;
+  std::string sourceMapFilename;
+  std::string sourceMapUrl;
   std::string symbolMap;
   bool emitBinary = true;
 
@@ -99,9 +101,15 @@ int main(int argc, const char *argv[]) {
            [&legalizeJavaScriptFFI](Options *o, const std::string &) {
              legalizeJavaScriptFFI = false;
            })
-      .add("--debuginfo", "-g", "Emit names section and debug info (for debug info you must emit text, -S, for this to work)",
+      .add("--debuginfo", "-g", "Emit names section in wasm binary (or full debuginfo in wast)",
            Options::Arguments::Zero,
            [&](Options *o, const std::string &arguments) { options.passOptions.debugInfo = true; })
+      .add("--source-map", "-sm", "Emit source map (if using binary output) to the specified file",
+           Options::Arguments::One,
+           [&sourceMapFilename](Options *o, const std::string &argument) { sourceMapFilename = argument; })
+      .add("--source-map-url", "-su", "Use specified string as source map URL",
+           Options::Arguments::One,
+           [&sourceMapUrl](Options *o, const std::string &argument) { sourceMapUrl = argument; })
       .add("--symbolmap", "-s", "Emit a symbol map (indexes => names)",
            Options::Arguments::One,
            [&](Options *o, const std::string &argument) { symbolMap = argument; })
@@ -136,8 +144,9 @@ int main(int argc, const char *argv[]) {
   }
 
   Asm2WasmPreProcessor pre;
-  // wasm binaries can contain a names section, but not full debug info
-  pre.debugInfo = options.passOptions.debugInfo && !emitBinary;
+  // wasm binaries can contain a names section, but not full debug info --
+  // debug info is disabled if a map file is not specified with wasm binary
+  pre.debugInfo = options.passOptions.debugInfo && (!emitBinary || sourceMapFilename.size());
   auto input(
       read_file<std::vector<char>>(options.extra["infile"], Flags::Text, options.debug ? Flags::Debug : Flags::Release));
   char *start = pre.process(input.data());
@@ -204,6 +213,10 @@ int main(int argc, const char *argv[]) {
   writer.setDebugInfo(options.passOptions.debugInfo);
   writer.setSymbolMap(symbolMap);
   writer.setBinary(emitBinary);
+  if (emitBinary) {
+    writer.setSourceMapFilename(sourceMapFilename);
+    writer.setSourceMapUrl(sourceMapUrl);
+  }
   writer.write(wasm, options.extra["output"]);
 
   if (options.debug) std::cerr << "done." << std::endl;
diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 067c0f28d..e8003a5ca 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -30,6 +30,8 @@ using namespace wasm;
 int main(int argc, const char *argv[]) {
   bool debugInfo = false;
   std::string symbolMap;
+  std::string sourceMapFilename;
+  std::string sourceMapUrl;
   Options options("wasm-as", "Assemble a .wast (WebAssembly text format) into a .wasm (WebAssembly binary format)");
   options.extra["validate"] = "wasm";
   options
@@ -51,6 +53,12 @@ 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("--source-map", "-sm", "Emit source map to the specified file",
+           Options::Arguments::One,
+           [&sourceMapFilename](Options *o, const std::string &argument) { sourceMapFilename = argument; })
+      .add("--source-map-url", "-su", "Use specified string as source map URL",
+           Options::Arguments::One,
+           [&sourceMapUrl](Options *o, const std::string &argument) { sourceMapUrl = argument; })
       .add("--symbolmap", "-s", "Emit a symbol map (indexes => names)",
            Options::Arguments::One,
            [&](Options *o, const std::string &argument) { symbolMap = argument; })
@@ -86,13 +94,23 @@ int main(int argc, const char *argv[]) {
   if (options.debug) std::cerr << "binarification..." << std::endl;
   BufferWithRandomAccess buffer(options.debug);
   WasmBinaryWriter writer(&wasm, buffer, options.debug);
-  writer.setDebugInfo(debugInfo);
+  // if debug info is used, then we want to emit the names section
+  writer.setNamesSection(debugInfo);
+  std::unique_ptr<std::ofstream> sourceMapStream = nullptr;
+  if (sourceMapFilename.size()) {
+    sourceMapStream = make_unique<std::ofstream>();
+    sourceMapStream->open(sourceMapFilename);
+    writer.setSourceMap(sourceMapStream.get(), sourceMapUrl);
+  }
   if (symbolMap.size() > 0) writer.setSymbolMap(symbolMap);
   writer.write();
 
   if (options.debug) std::cerr << "writing to output..." << std::endl;
   Output output(options.extra["output"], Flags::Binary, options.debug ? Flags::Debug : Flags::Release);
   buffer.writeTo(output);
+  if (sourceMapStream) {
+    sourceMapStream->close();
+  }
 
   if (options.debug) std::cerr << "Done." << std::endl;
 }
diff --git a/src/tools/wasm-dis.cpp b/src/tools/wasm-dis.cpp
index 93c286913..e6fd7badd 100644
--- a/src/tools/wasm-dis.cpp
+++ b/src/tools/wasm-dis.cpp
@@ -28,6 +28,7 @@ using namespace cashew;
 using namespace wasm;
 
 int main(int argc, const char *argv[]) {
+  std::string sourceMapFilename;
   Options options("wasm-dis", "Un-assemble a .wasm (WebAssembly binary format) into a .wast (WebAssembly text format)");
   options.add("--output", "-o", "Output file (stdout if not specified)",
               Options::Arguments::One,
@@ -35,6 +36,9 @@ int main(int argc, const char *argv[]) {
                 o->extra["output"] = argument;
                 Colors::disable();
               })
+      .add("--source-map", "-sm", "Consume source map from the specified file to add location information",
+           Options::Arguments::One,
+           [&sourceMapFilename](Options *o, const std::string &argument) { sourceMapFilename = argument; })
       .add_positional("INFILE", Options::Arguments::One,
                       [](Options *o, const std::string &argument) {
                         o->extra["infile"] = argument;
@@ -46,11 +50,23 @@ int main(int argc, const char *argv[]) {
   if (options.debug) std::cerr << "parsing binary..." << std::endl;
   Module wasm;
   try {
+    std::unique_ptr<std::ifstream> sourceMapStream;
     WasmBinaryBuilder parser(wasm, input, options.debug);
+    if (sourceMapFilename.size()) {
+        sourceMapStream = make_unique<std::ifstream>();
+        sourceMapStream->open(sourceMapFilename);
+        parser.setDebugLocations(sourceMapStream.get());
+    }
     parser.read();
+    if (sourceMapStream) {
+        sourceMapStream->close();
+    }
   } catch (ParseException& p) {
     p.dump(std::cerr);
     Fatal() << "error in parsing wasm binary";
+  } catch (MapParseException& p) {
+    p.dump(std::cerr);
+    Fatal() << "error in parsing wasm source mapping";
   }
 
   if (options.debug) std::cerr << "Printing..." << std::endl;