Reland emitting of DataCount section (#2027)

This reverts commit cb2d63586c08a3dd194d2b733ceb3f5051c081f8.
The issues with feature validation were mostly resolved in #1993, and
this PR finishes the job by adding feature flags to wasm-as to avoid
emitting the DataCount section when bulk-memory is not enabled.

2 files changed, 6 insertions, 11 deletions

diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index fb79eb7cf..20e51e31f 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -19,12 +19,12 @@
 //
 
 #include "support/colors.h"
-#include "support/command-line.h"
 #include "support/file.h"
 #include "wasm-io.h"
 #include "wasm-s-parser.h"
 #include "wasm-validator.h"
 
+#include "tool-options.h"
 #include "tool-utils.h"
 
 using namespace cashew;
@@ -35,7 +35,7 @@ int main(int argc, const char *argv[]) {
   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)");
+  ToolOptions options("wasm-as", "Assemble a .wast (WebAssembly text format) into a .wasm (WebAssembly binary format)");
   options.extra["validate"] = "wasm";
   options
       .add("--output", "-o", "Output file (stdout if not specified)",
@@ -91,7 +91,7 @@ int main(int argc, const char *argv[]) {
     Fatal() << "error in parsing input";
   }
 
-  wasm.features = FeatureSet::All;
+  options.applyFeatures(wasm);
 
   if (options.extra["validate"] != "none") {
     if (options.debug) std::cerr << "Validating..." << std::endl;
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index d6091e93c..f3642203d 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -317,14 +317,9 @@ void WasmBinaryWriter::writeDataCount() {
   if (!wasm->features.hasBulkMemory() || !wasm->memory.segments.size()) {
     return;
   }
-
-  // TODO(tlively): re-enable writing the data count once the default feature
-  // set is no longer All, which causes validation errors in Emscripten due to
-  // the presence of an unrecognized section.
-
-  // auto start = startSection(BinaryConsts::Section::DataCount);
-  // o << U32LEB(wasm->memory.segments.size());
-  // finishSection(start);
+  auto start = startSection(BinaryConsts::Section::DataCount);
+  o << U32LEB(wasm->memory.segments.size());
+  finishSection(start);
 }
 
 void WasmBinaryWriter::writeDataSegments() {