Check for redefinitions of elem segments (#1193)

Fixes: #1187

4 files changed, 26 insertions, 4 deletions

diff --git a/src/resolve-names.cc b/src/resolve-names.cc
index 1bcc52e6..0e3c70e1 100644
--- a/src/resolve-names.cc
+++ b/src/resolve-names.cc
@@ -461,6 +461,7 @@ void NameResolver::VisitDataSegment(DataSegment* segment) {
 
 Result NameResolver::VisitModule(Module* module) {
   current_module_ = module;
+  CheckDuplicateBindings(&module->elem_segment_bindings, "elem");
   CheckDuplicateBindings(&module->func_bindings, "function");
   CheckDuplicateBindings(&module->global_bindings, "global");
   CheckDuplicateBindings(&module->func_type_bindings, "function type");
diff --git a/src/wast-parser.cc b/src/wast-parser.cc
index 517b70bc..ca21584f 100644
--- a/src/wast-parser.cc
+++ b/src/wast-parser.cc
@@ -932,9 +932,17 @@ Result WastParser::ParseElemModuleField(Module* module) {
   EXPECT(Lpar);
   Location loc = GetLocation();
   EXPECT(Elem);
-  std::string name;
-  ParseBindVarOpt(&name);
-  auto field = MakeUnique<ElemSegmentModuleField>(loc, name);
+  std::string segment_name;
+  ParseBindVarOpt(&segment_name);
+  // With MVP text format the name here was intended to refer to the table
+  // that the elem segment was part of, but we never did anything with this name
+  // since there was only one table anyway.
+  // With bulk-memory enabled this introduces a new name for the particualr
+  // elem segment.
+  if (!options_->features.bulk_memory_enabled()) {
+    segment_name = "";
+  }
+  auto field = MakeUnique<ElemSegmentModuleField>(loc, segment_name);
 
   if (ParseRefTypeOpt(&field->elem_segment.elem_type)) {
     field->elem_segment.passive = true;
diff --git a/test/parse/expr/bulk-memory-named.txt b/test/parse/expr/bulk-memory-named.txt
index 22a94d2f..92af32d3 100644
--- a/test/parse/expr/bulk-memory-named.txt
+++ b/test/parse/expr/bulk-memory-named.txt
@@ -11,7 +11,7 @@
 
   (table 1 anyfunc)
   (elem $elem funcref (ref.func 0) (ref.null))
-  (elem $elem funcref 0)
+  (elem $elem2 funcref 0)
   (func
     i32.const 0 i32.const 0 i32.const 0 table.init $elem
     elem.drop $elem
diff --git a/test/parse/module/bad-elem-redefinition.txt b/test/parse/module/bad-elem-redefinition.txt
new file mode 100644
index 00000000..1b589617
--- /dev/null
+++ b/test/parse/module/bad-elem-redefinition.txt
@@ -0,0 +1,13 @@
+;;; TOOL: wat2wasm
+;;; ARGS: --enable-bulk-memory
+;;; ERROR: 1
+(module
+  (elem $elem funcref 0)
+  (elem $elem funcref 0)
+  (func))
+
+(;; STDERR ;;;
+out/test/parse/module/bad-elem-redefinition.txt:6:4: error: redefinition of elem "$elem"
+  (elem $elem funcref 0)
+   ^^^^
+;;; STDERR ;;)