[libc++][test] Avoid -Wunused-variable warnings in mutex tests

[StephanTLavavej]

After enhancing MSVC's STL to statically initialize our condition_variable, Clang began noticing that these mutex flavors were unused:

[...snipped...]\default.pass.cpp(23,22): error: unused variable 'm' [-Werror,-Wunused-variable]
   23 |     std::timed_mutex m;
      |                      ^

[...snipped...]\default.pass.cpp(23,32): error: unused variable 'm' [-Werror,-Wunused-variable]
   23 |     std::recursive_timed_mutex m;
      |                                ^

[...snipped...]\default.pass.cpp(24,29): error: unused variable 'm' [-Werror,-Wunused-variable]
   24 |     std::shared_timed_mutex m;
      |                             ^

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Stephan T. Lavavej (StephanTLavavej)

Changes

After enhancing MSVC's STL to statically initialize our condition_variable, Clang began noticing that these mutex flavors were unused:

[...snipped...]\default.pass.cpp(23,22): error: unused variable 'm' [-Werror,-Wunused-variable]
   23 |     std::timed_mutex m;
      |                      ^

[...snipped...]\default.pass.cpp(23,32): error: unused variable 'm' [-Werror,-Wunused-variable]
   23 |     std::recursive_timed_mutex m;
      |                                ^

[...snipped...]\default.pass.cpp(24,29): error: unused variable 'm' [-Werror,-Wunused-variable]
   24 |     std::shared_timed_mutex m;
      |                             ^

---

Full diff: https://github.com/llvm/llvm-project/pull/94907.diff

3 Files Affected:

• (modified) libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/default.pass.cpp (+3-3)
• (modified) libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/default.pass.cpp (+3-3)
• (modified) libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/default.pass.cpp (+3-3)

diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/default.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/default.pass.cpp
index b278419df6eed..7a8d096994fff 100644
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/default.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/default.pass.cpp
@@ -19,9 +19,9 @@
 
 #include "test_macros.h"
 
-int main(int, char**)
-{
-    std::shared_timed_mutex m;
+int main(int, char**) {
+  std::shared_timed_mutex m;
+  (void)m;
 
   return 0;
 }
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/default.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/default.pass.cpp
index d13a0ad435aea..c7f207372ac42 100644
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/default.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/default.pass.cpp
@@ -18,9 +18,9 @@
 
 #include "test_macros.h"
 
-int main(int, char**)
-{
-    std::timed_mutex m;
+int main(int, char**) {
+  std::timed_mutex m;
+  (void)m;
 
   return 0;
 }
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/default.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/default.pass.cpp
index 73e2e7a3a5ab9..3096e031855a2 100644
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/default.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/default.pass.cpp
@@ -18,9 +18,9 @@
 
 #include "test_macros.h"
 
-int main(int, char**)
-{
-    std::recursive_timed_mutex m;
+int main(int, char**) {
+  std::recursive_timed_mutex m;
+  (void)m;
 
   return 0;
 }