Don't generate a bare "$" from an empty export name

src/generate-names.cc

@@ -179,6 +179,12 @@ void NameGenerator::MaybeUseAndBindName(BindingHash* bindings,
                                         Index index,
                                         std::string* str) {
   if (!HasName(*str)) {
+    if (!HasName(name)) {
+      // An empty import or export name would produce a bare "$", which is not
+      // a valid identifier. Leave the name unset; the index-based pass that
+      // runs afterwards will give it a usable one.
+      return;
+    }
     unsigned disambiguator = 0;
     while (true) {
       GenerateName(name, kInvalidIndex, disambiguator, str);

test/roundtrip/generate-empty-export-name.txt

@@ -0,0 +1,22 @@
+;;; TOOL: run-roundtrip
+;;; ARGS: --stdout --generate-names
+
+(module
+  ;; With no name section the generated names come from the exports. An empty
+  ;; export name cannot be used as an identifier, since it would produce a bare
+  ;; "$", so it has to be skipped: this func has no other export to take a name
+  ;; from and falls back to an index-based name.
+  (func $f)
+  (export "" (func $f))
+
+  (func $g)
+  (export "named" (func $g))
+)
+(;; STDOUT ;;;
+(module
+  (type $t0 (func))
+  (func $f0 (type $t0))
+  (func $named (type $t0))
+  (export "" (func $f0))
+  (export "named" (func $named)))
+;;; STDOUT ;;)

test/wasm2c/export-names.txt

@@ -926,7 +926,7 @@ DEFINE_TABLE_FILL(externref)
                                   wasm_rt_tailcallee_t* next)
 #endif
 
-static void w2c_test__0(w2c_test*);
+static void w2c_test_0x2A0x2F_0(w2c_test*);
 
 FUNC_TYPE_T(w2c_test_t0) = "\x36\xa9\xe7\xf1\xc9\x5b\x82\xff\xb9\x97\x43\xe0\xc5\xc4\xce\x95\xd8\x3c\x9a\x43\x0a\xac\x59\xf8\x4e\xf3\xcb\xfa\xb6\x14\x50\x68";
 
@@ -941,7 +941,7 @@ void w2c_test_(w2c_test* instance) {
 #endif
   wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
-  w2c_test__0(instance);
+  w2c_test_0x2A0x2F_0(instance);
 #if WASM_RT_USE_SEGUE_FOR_THIS_MODULE && !WASM_RT_SEGUE_FREE_SEGMENT
   wasm_rt_segue_write_base(segue_saved_base);
 #endif
@@ -955,7 +955,7 @@ void w2c_test_0x2A0x2F(w2c_test* instance) {
 #endif
   wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
-  w2c_test__0(instance);
+  w2c_test_0x2A0x2F_0(instance);
 #if WASM_RT_USE_SEGUE_FOR_THIS_MODULE && !WASM_RT_SEGUE_FREE_SEGMENT
   wasm_rt_segue_write_base(segue_saved_base);
 #endif
@@ -969,7 +969,7 @@ void w2c_test_0x3F0x3F0x2F(w2c_test* instance) {
 #endif
   wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
-  w2c_test__0(instance);
+  w2c_test_0x2A0x2F_0(instance);
 #if WASM_RT_USE_SEGUE_FOR_THIS_MODULE && !WASM_RT_SEGUE_FREE_SEGMENT
   wasm_rt_segue_write_base(segue_saved_base);
 #endif
@@ -983,7 +983,7 @@ void w2c_test_0x0A(w2c_test* instance) {
 #endif
   wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
-  w2c_test__0(instance);
+  w2c_test_0x2A0x2F_0(instance);
 #if WASM_RT_USE_SEGUE_FOR_THIS_MODULE && !WASM_RT_SEGUE_FREE_SEGMENT
   wasm_rt_segue_write_base(segue_saved_base);
 #endif
@@ -997,7 +997,7 @@ void w2c_test_0xE20x9D0xA40xEF0xB80x8F(w2c_test* instance) {
 #endif
   wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
-  w2c_test__0(instance);
+  w2c_test_0x2A0x2F_0(instance);
 #if WASM_RT_USE_SEGUE_FOR_THIS_MODULE && !WASM_RT_SEGUE_FREE_SEGMENT
   wasm_rt_segue_write_base(segue_saved_base);
 #endif
@@ -1045,7 +1045,7 @@ wasm_rt_func_type_t wasm2c_test_get_func_type(uint32_t param_count, uint32_t res
   return NULL;
 }
 
-void w2c_test__0(w2c_test* instance) {
+void w2c_test_0x2A0x2F_0(w2c_test* instance) {
   FUNC_PROLOGUE;
   uint8_t* const wasm_rt_local_memory_base = (instance->w2c_0x5Cmodule_import0x200x2A0x2F)->data;
   uint64_t wasm_rt_local_memory_size = (instance->w2c_0x5Cmodule_import0x200x2A0x2F)->size;