From a1fb44a3321582309cecd29f3dc261bcac77a7eb Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Wed, 5 Aug 2026 11:30:46 -0700
Subject: [PATCH] Add BYN_WARN_UNUSED macro and apply to Name and IString

Define `BYN_WARN_UNUSED` using `[[gnu::warn_unused]]` for GCC/Clang
and fallback for other compilers. Annotating `IString` and `Name` with
this attribute allows compilers to report unused variable diagnostics
for default-constructed instances regardless of non-trivial constructors.

Followup to #8972.

Once this lands we can extend this to other types to get better
coverage.
---
 src/compiler-support.h       | 6 ++++++
 src/ir/possible-contents.cpp | 1 -
 src/support/istring.h        | 2 +-
 src/support/name.h           | 2 +-
 src/tools/wasm-opt.cpp       | 1 -
 5 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/compiler-support.h b/src/compiler-support.h
index a3485919086..3082ab3dfa1 100644
--- a/src/compiler-support.h
+++ b/src/compiler-support.h
@@ -31,4 +31,10 @@
 #define WASM_BUILTIN_UNREACHABLE __assume(false)
 #endif
 
+#if defined(__GNUC__) || defined(__clang__)
+#define BYN_WARN_UNUSED [[gnu::warn_unused]]
+#else
+#define BYN_WARN_UNUSED
+#endif
+
 #endif // wasm_compiler_support_h
diff --git a/src/ir/possible-contents.cpp b/src/ir/possible-contents.cpp
index f5bdb46fc09..f752fa10172 100644
--- a/src/ir/possible-contents.cpp
+++ b/src/ir/possible-contents.cpp
@@ -898,7 +898,6 @@ struct InfoCollector
   }
 
   void visitCall(Call* curr) {
-    Name targetName;
     if (!Intrinsics(*getModule()).isCallWithoutEffects(curr)) {
       // This is just a normal call.
       handleDirectCall(curr, curr->target);
diff --git a/src/support/istring.h b/src/support/istring.h
index bc7d2380dd2..458c8b47c6e 100644
--- a/src/support/istring.h
+++ b/src/support/istring.h
@@ -31,7 +31,7 @@
 
 namespace wasm {
 
-struct IString {
+struct BYN_WARN_UNUSED IString {
 private:
   static const char* interned(std::string_view s);
 
diff --git a/src/support/name.h b/src/support/name.h
index d6c71f732c9..2d22f8ad1cb 100644
--- a/src/support/name.h
+++ b/src/support/name.h
@@ -31,7 +31,7 @@ namespace wasm {
 // TODO: as an optimization, IString values < some threshold could be considered
 //       numerical indices directly.
 
-struct Name : public IString {
+struct BYN_WARN_UNUSED Name : public IString {
   Name() : IString() {}
   Name(std::string_view str) : IString(str) {}
   Name(const char* str) : IString(str) {}
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index ef85804963c..94d72181cac 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -74,7 +74,6 @@ willRemoveDebugInfo(const std::vector<OptimizationOptions::PassInfo>& passes) {
 //
 
 int main(int argc, const char* argv[]) {
-  Name entry;
   bool emitBinary = true;
   bool converge = false;
   bool fuzzExecBefore = false;