[wasm-gc][inspector] Fix handling of very long type names

And also make sure that even long names don't get truncated.

Fixed: chromium:1216284
Change-Id: I2792b60ddeb40a87816cb54fb0414ef0dea45da0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2947409
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75059}

src/debug/debug-wasm-objects.cc

@@ -767,8 +767,12 @@ Handle<String> WasmSimd128ToString(Isolate* isolate, wasm::Simd128 s128) {
 
 Handle<String> GetRefTypeName(Isolate* isolate, wasm::ValueType type,
                               wasm::NativeModule* module) {
-  const char* nullable = type.kind() == wasm::kOptRef ? " null" : "";
-  EmbeddedVector<char, 64> type_name;
+  bool is_nullable = type.kind() == wasm::kOptRef;
+  const char* null_str = is_nullable ? " null" : "";
+  // This length only needs to be enough for generated names like
+  // "(ref null $type12345)". For names coming from the name section,
+  // we'll dynamically allocate an appropriately sized vector.
+  EmbeddedVector<char, 32> type_name;
   size_t len;
   if (type.heap_type().is_generic()) {
     const char* generic_name = "";
@@ -795,23 +799,32 @@ Handle<String> GetRefTypeName(Isolate* isolate, wasm::ValueType type,
       default:
         UNREACHABLE();
     }
-    len = SNPrintF(type_name, "(ref%s %s)", nullable, generic_name);
+    len = SNPrintF(type_name, "(ref%s %s)", null_str, generic_name);
   } else {
     int type_index = type.ref_index();
     wasm::ModuleWireBytes module_wire_bytes(module->wire_bytes());
     Vector<const char> name_vec = module_wire_bytes.GetNameOrNull(
         module->GetDebugInfo()->GetTypeName(type_index));
     if (name_vec.empty()) {
-      len = SNPrintF(type_name, "(ref%s $type%u)", nullable, type_index);
+      len = SNPrintF(type_name, "(ref%s $type%u)", null_str, type_index);
     } else {
-      len = SNPrintF(type_name, "(ref%s $", nullable);
-      Vector<char> suffix = type_name.SubVector(len, type_name.size());
+      size_t required_length =
+          name_vec.size() +       // length of provided name
+          7 +                     // length of "(ref $)"
+          (is_nullable ? 5 : 0);  // length of " null" (optional)
+      Vector<char> long_type_name = Vector<char>::New(required_length);
+      len = SNPrintF(long_type_name, "(ref%s $", null_str);
+      Vector<char> suffix =
+          long_type_name.SubVector(len, long_type_name.size());
+      // StrNCpy requires that there is room for an assumed trailing \0...
+      DCHECK_EQ(suffix.size(), name_vec.size() + 1);
       StrNCpy(suffix, name_vec.data(), name_vec.size());
-      len += std::min(suffix.size(), name_vec.size());
-      if (len < type_name.size()) {
-        type_name[len] = ')';
-        len++;
-      }
+      // ...but we actually write ')' into that byte.
+      long_type_name[required_length - 1] = ')';
+      Handle<String> result =
+          isolate->factory()->InternalizeString(long_type_name);
+      long_type_name.Dispose();
+      return result;
     }
   }
   return isolate->factory()->InternalizeString(type_name.SubVector(0, len));

test/inspector/debugger/wasm-gc-breakpoints-expected.txt

@@ -3,10 +3,10 @@ Tests GC object inspection.
 Running test: test
 Instantiating.
 Waiting for wasm script (ignoring first non-wasm script).
-Setting breakpoint at offset 107 on script wasm://wasm/22e4830a
+Setting breakpoint at offset 107 on script wasm://wasm/151aafd6
 Calling main()
 Paused:
-Script wasm://wasm/22e4830a byte offset 107: Wasm opcode 0x21 (kExprLocalSet)
+Script wasm://wasm/151aafd6 byte offset 107: Wasm opcode 0x21 (kExprLocalSet)
 Scope:
 at $main (0:107):
  - scope (wasm-expression-stack):
@@ -20,7 +20,7 @@ at $main (0:107):
      object details:
    $byte: 127 (i8)
    $word: 32767 (i16)
-   $pointer: Struct ((ref $StrB))
+   $pointer: Struct ((ref $veryLongNameWithMoreThanOneHundredAndTwentyEightCharactersToTestThatWeAreHandlingStringBufferOverflowWithoutCrashing_ThisWontGetTruncated))
  - scope (module):
    instance: exports: "main" (Function)
    module: Module

test/inspector/debugger/wasm-gc-breakpoints.js

@@ -86,7 +86,7 @@ const module_bytes = [
 
   /////////////////////////// NAME SECTION //////////////////////////
   0x00,  // name section
-  0x4d,  // section length
+  0xd4, 0x01, // section length
   0x04,  // length of "name"
   0x6e, 0x61, 0x6d, 0x65,  // "name"
 
@@ -103,14 +103,27 @@ const module_bytes = [
   0x76, 0x61, 0x72, 0x42,  // "varB"
 
   0x04,  // "type names" subsection
-  0x13,  // length of subsection
+  0x99, 0x01,  // length of subsection
   0x03,  // number of entries
   0x00,  // type index
   0x04,  // name length
   0x53, 0x74, 0x72, 0x41,  // "StrA"
   0x01,  // type index
-  0x04,  // name length
-  0x53, 0x74, 0x72, 0x42,  // "StrB"
+  0x89, 0x01,  // name length
+  // Called "$StrB" in other comments, actual name:
+  // "veryLongNameWithMoreThanOneHundredAndTwentyEightCharactersToTestThat
+  // WeAreHandlingStringBufferOverflowWithoutCrashing_ThisWontGetTruncated"
+  0x76, 0x65, 0x72, 0x79, 0x4c, 0x6f, 0x6e, 0x67, 0x4e, 0x61, 0x6d, 0x65, 0x57,
+  0x69, 0x74, 0x68, 0x4d, 0x6f, 0x72, 0x65, 0x54, 0x68, 0x61, 0x6e, 0x4f, 0x6e,
+  0x65, 0x48, 0x75, 0x6e, 0x64, 0x72, 0x65, 0x64, 0x41, 0x6e, 0x64, 0x54, 0x77,
+  0x65, 0x6e, 0x74, 0x79, 0x45, 0x69, 0x67, 0x68, 0x74, 0x43, 0x68, 0x61, 0x72,
+  0x61, 0x63, 0x74, 0x65, 0x72, 0x73, 0x54, 0x6f, 0x54, 0x65, 0x73, 0x74, 0x54,
+  0x68, 0x61, 0x74, 0x57, 0x65, 0x41, 0x72, 0x65, 0x48, 0x61, 0x6e, 0x64, 0x6c,
+  0x69, 0x6e, 0x67, 0x53, 0x74, 0x72, 0x69, 0x6e, 0x67, 0x42, 0x75, 0x66, 0x66,
+  0x65, 0x72, 0x4f, 0x76, 0x65, 0x72, 0x66, 0x6c, 0x6f, 0x77, 0x57, 0x69, 0x74,
+  0x68, 0x6f, 0x75, 0x74, 0x43, 0x72, 0x61, 0x73, 0x68, 0x69, 0x6e, 0x67, 0x5f,
+  0x54, 0x68, 0x69, 0x73, 0x57, 0x6f, 0x6e, 0x74, 0x47, 0x65, 0x74, 0x54, 0x72,
+  0x75, 0x6e, 0x63, 0x61, 0x74, 0x65, 0x64,
   0x02,  // type index
   0x04,  // name length
   0x41, 0x72, 0x72, 0x43,  // "ArrC"