3 files changed, 10 insertions, 3 deletions
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index f2c74221d..42fc1e4db 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -224,7 +224,10 @@ int main(int argc, const char *argv[]) {
   // for metadata).
   if (!dataSegmentFile.empty()) {
     Output memInitFile(dataSegmentFile, Flags::Binary, Flags::Release);
-    generator.separateDataSegments(&memInitFile);
+    if (globalBase == INVALID_BASE) {
+      Fatal() << "globalBase must be set";
+    }
+    generator.separateDataSegments(&memInitFile, globalBase);
   }
 
   if (options.debug) {
diff --git a/src/wasm-emscripten.h b/src/wasm-emscripten.h
index d078cafbf..275c809fd 100644
--- a/src/wasm-emscripten.h
+++ b/src/wasm-emscripten.h
@@ -57,7 +57,10 @@ public:
 
   void fixInvokeFunctionNames();
 
-  void separateDataSegments(Output* outfile);
+  // Emits the data segments to a file. The file contains data from address base
+  // onwards (we must pass in base, as we can't tell it from the wasm - the first
+  // segment may start after a run of zeros, but we need those zeros in the file).
+  void separateDataSegments(Output* outfile, Address base);
 
 private:
   Module& wasm;
diff --git a/src/wasm/wasm-emscripten.cpp b/src/wasm/wasm-emscripten.cpp
index e09ad98d2..a383a812a 100644
--- a/src/wasm/wasm-emscripten.cpp
+++ b/src/wasm/wasm-emscripten.cpp
@@ -919,10 +919,11 @@ std::string EmscriptenGlueGenerator::generateEmscriptenMetadata(
   return meta.str();
 }
 
-void EmscriptenGlueGenerator::separateDataSegments(Output* outfile) {
+void EmscriptenGlueGenerator::separateDataSegments(Output* outfile, Address base) {
   size_t lastEnd = 0;
   for (Memory::Segment& seg : wasm.memory.segments) {
     size_t offset = seg.offset->cast<Const>()->value.geti32();
+    offset -= base;
     size_t fill = offset - lastEnd;
     if (fill > 0) {
       std::vector<char> buf(fill);