[libcxx-commits] [libcxx] [libc++] Avoid relying on CTAD for std::lock_guard in the benchmarks (PR #225503)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne created https://github.com/llvm/llvm-project/pull/225503

libc++ provides a deduction guide for std::lock_guard, but libstdc++ does not, so the code trips -Wctad-maybe-unsupported when the benchmark is built against libstdc++.

>From 28e959d5150b21e2ba982bb21f1814a5144c4806 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Tue, 22 Sep 2026 12:31:15 -0700
Subject: [PATCH] [libc++] Avoid relying on CTAD for std::lock_guard in the
 benchmarks

libc++ provides a deduction guide for std::lock_guard, but libstdc++
does not, so the code trips -Wctad-maybe-unsupported when the benchmark
is built against libstdc++.
---
 libcxx/test/benchmarks/stringstream.bench.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libcxx/test/benchmarks/stringstream.bench.cpp b/libcxx/test/benchmarks/stringstream.bench.cpp
index 052696815236d4..123727a3b49886 100644
--- a/libcxx/test/benchmarks/stringstream.bench.cpp
+++ b/libcxx/test/benchmarks/stringstream.bench.cpp
@@ -39,7 +39,7 @@ struct LocaleSelector {
   static std::mutex mutex;
 
   LocaleSelector(benchmark::State& state) {
-    std::lock_guard guard(mutex);
+    std::lock_guard<std::mutex> guard(mutex);
     switch (state.range(0)) {
     case 0: {
       old   = std::locale::global(std::locale::classic());
@@ -67,7 +67,7 @@ struct LocaleSelector {
   }
 
   ~LocaleSelector() {
-    std::lock_guard guard(mutex);
+    std::lock_guard<std::mutex> guard(mutex);
     std::locale::global(old);
   }
 };