[libcxx-commits] [libcxx] [libc++][test] Fix Clang `-Wunused-variable` warnings in time.zone.members/to_sys.pass.cpp (PR #100504)

[Stephan T. Lavavej via libcxx-commits]

https://github.com/StephanTLavavej created https://github.com/llvm/llvm-project/pull/100504

Recently introduced by @mordante's #90394. This newly added test contains code like:

https://github.com/llvm/llvm-project/blob/ccae7b461be339e717d02f99ac857cf0bc7d17fc/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp#L89-L101

The usage in `TEST_LIBCPP_REQUIRE` is libc++-specific, which expands to nothing for MSVC's STL. That's good, but any variables that are only used within libc++-specific test code need to be marked as `[[maybe_unused]]`. The `std::string_view what` isn't, emitting warnings:

```
D:\GitHub\STL\llvm-project\libcxx\test\std\time\time.zone\time.zone.timezone\time.zone.members\to_sys.pass.cpp(92,26): error: unused variable 'what' [-Werror,-Wunused-variable]
   92 |         std::string_view what =
      |                          ^~~~
D:\GitHub\STL\llvm-project\libcxx\test\support\assert_macros.h(136,9): note: expanded from macro 'TEST_VALIDATE_EXCEPTION'
  136 |         PRED(EXCEPTION);                                                                                               \
      |         ^~~~
```

>From 9b207acffb978f9336187768e575036277ec127f Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl at nuwen.net>
Date: Wed, 24 Jul 2024 19:54:50 -0700
Subject: [PATCH] Fix Clang `-Wunused-variable` warnings.

---
 .../time.zone.members/to_sys.pass.cpp            | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp
index 874c3d52e460b..e32b6d523d0ed 100644
--- a/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp
+++ b/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp
@@ -89,7 +89,7 @@ static void test_nonexistent() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::nonexistent_local_time,
       [&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-03-30 02:30:00.000000000 is in a gap between
 1986-03-30 02:00:00 CET and
 1986-03-30 03:00:00 CEST which are both equivalent to
@@ -103,7 +103,7 @@ static void test_nonexistent() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::nonexistent_local_time,
       [&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-03-30 02:30:00.000000 is in a gap between
 1986-03-30 02:00:00 CET and
 1986-03-30 03:00:00 CEST which are both equivalent to
@@ -117,7 +117,7 @@ static void test_nonexistent() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::nonexistent_local_time,
       [&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-03-30 02:30:00.000 is in a gap between
 1986-03-30 02:00:00 CET and
 1986-03-30 03:00:00 CEST which are both equivalent to
@@ -131,7 +131,7 @@ static void test_nonexistent() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::nonexistent_local_time,
       [&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-03-30 02:30:00 is in a gap between
 1986-03-30 02:00:00 CET and
 1986-03-30 03:00:00 CEST which are both equivalent to
@@ -173,7 +173,7 @@ static void test_ambiguous() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::ambiguous_local_time,
       [&]([[maybe_unused]] const std::chrono::ambiguous_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-09-28 02:30:00.000000000 is ambiguous.  It could be
 1986-09-28 02:30:00.000000000 CEST == 1986-09-28 00:30:00.000000000 UTC or
 1986-09-28 02:30:00.000000000 CET == 1986-09-28 01:30:00.000000000 UTC)";
@@ -186,7 +186,7 @@ static void test_ambiguous() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::ambiguous_local_time,
       [&]([[maybe_unused]] const std::chrono::ambiguous_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-09-28 02:30:00.000000 is ambiguous.  It could be
 1986-09-28 02:30:00.000000 CEST == 1986-09-28 00:30:00.000000 UTC or
 1986-09-28 02:30:00.000000 CET == 1986-09-28 01:30:00.000000 UTC)";
@@ -199,7 +199,7 @@ static void test_ambiguous() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::ambiguous_local_time,
       [&]([[maybe_unused]] const std::chrono::ambiguous_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-09-28 02:30:00.000 is ambiguous.  It could be
 1986-09-28 02:30:00.000 CEST == 1986-09-28 00:30:00.000 UTC or
 1986-09-28 02:30:00.000 CET == 1986-09-28 01:30:00.000 UTC)";
@@ -212,7 +212,7 @@ static void test_ambiguous() {
   TEST_VALIDATE_EXCEPTION(
       std::chrono::ambiguous_local_time,
       [&]([[maybe_unused]] const std::chrono::ambiguous_local_time& e) {
-        std::string_view what =
+        [[maybe_unused]] std::string_view what =
             R"(1986-09-28 02:30:00 is ambiguous.  It could be
 1986-09-28 02:30:00 CEST == 1986-09-28 00:30:00 UTC or
 1986-09-28 02:30:00 CET == 1986-09-28 01:30:00 UTC)";