[libc++][test] Fix Clang -Wunused-variable warnings in time.zone.members/to_sys.pass.cpp

[StephanTLavavej]

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

llvm-project/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp

Lines 89 to 101 in ccae7b4

	TEST_VALIDATE_EXCEPTION(
	std::chrono::nonexistent_local_time,
	[&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
	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
	1986-03-30 01:00:00 UTC)";
	TEST_LIBCPP_REQUIRE(
	e.what() == what,
	TEST_WRITE_CONCATENATED("Expected exception\n", what, "\n\nActual exception\n", e.what(), '\n'));
	},
	tz->to_sys(time + 0ns));

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);                                                                                               \
      |         ^~~~

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Stephan T. Lavavej (StephanTLavavej)

Changes

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

llvm-project/libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp

Lines 89 to 101 in ccae7b4

	TEST_VALIDATE_EXCEPTION(
	std::chrono::nonexistent_local_time,
	[&]([[maybe_unused]] const std::chrono::nonexistent_local_time& e) {
	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
	1986-03-30 01:00:00 UTC)";
	TEST_LIBCPP_REQUIRE(
	e.what() == what,
	TEST_WRITE_CONCATENATED("Expected exception\n", what, "\n\nActual exception\n", e.what(), '\n'));
	},
	tz->to_sys(time + 0ns));

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);                                                                                               \
      |         ^~~~

---

Full diff: https://github.com/llvm/llvm-project/pull/100504.diff

1 Files Affected:

• (modified) libcxx/test/std/time/time.zone/time.zone.timezone/time.zone.members/to_sys.pass.cpp (+8-8)

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)";

[mordante]

Thanks! LGTM!