[libc++][test] Fix simple warnings (#74186)

Found while running libc++'s tests with MSVC's STL. This fixes 3 kinds of warnings:

- Add void-casts to fix `-Wunused-variable` warnings.
- Avoid sign/truncation warnings in `ConvertibleToIntegral.h`.
- Add `TEST_STD_AT_LEAST_23_OR_RUNTIME_EVALUATED` to avoid mixing preprocessor 
  and runtime tests.
- Cleanup: Add `TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED` for
  consistency.

14 files changed, 35 insertions, 20 deletions

diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp
index ce5cf05..b1ad687 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp
@@ -94,7 +94,7 @@ struct Test1OutIters {
 
 TEST_CONSTEXPR_CXX20 bool test() {
   types::for_each(types::cpp17_input_iterator_list<int*>(), TestOutIters());
-  if (TEST_STD_VER >= 23 || !TEST_IS_CONSTANT_EVALUATED)
+  if (TEST_STD_AT_LEAST_23_OR_RUNTIME_EVALUATED)
     types::for_each(types::cpp17_input_iterator_list<std::unique_ptr<int>*>(), Test1OutIters());
 
   { // Make sure that padding bits aren't copied
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp
index 2ed4d37..61dea47 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp
@@ -92,7 +92,7 @@ struct Test1OutIters {
 
 TEST_CONSTEXPR_CXX20 bool test() {
   types::for_each(types::bidirectional_iterator_list<int*>(), TestOutIters());
-  if (TEST_STD_VER >= 23 || !TEST_IS_CONSTANT_EVALUATED)
+  if (TEST_STD_AT_LEAST_23_OR_RUNTIME_EVALUATED)
     types::for_each(types::bidirectional_iterator_list<std::unique_ptr<int>*>(), Test1OutIters());
 
   { // Make sure that padding bits aren't copied
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp
index cc832fe..904100c 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp
@@ -38,7 +38,7 @@ struct Test {
 TEST_CONSTEXPR_CXX20 bool test() {
   types::for_each(types::cpp17_input_iterator_list<const int*>(), Test());
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     std::vector<bool> vec(256 + 64);
     for (ptrdiff_t i = 0; i != 256; ++i) {
       for (size_t offset = 0; offset != 64; ++offset) {
diff --git a/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h b/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
index 470f5d8..0ca5c33 100644
--- a/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
+++ b/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
@@ -16,8 +16,8 @@ struct IntType {
 
   constexpr bool operator==(const IntType& rhs) const { return val == rhs.val; }
   constexpr operator int() const noexcept { return val; }
-  constexpr operator unsigned char() const { return val; }
-  constexpr operator signed char() const noexcept { return val; }
+  constexpr operator unsigned char() const { return static_cast<unsigned char>(val); }
+  constexpr operator signed char() const noexcept { return static_cast<signed char>(val); }
 };
 
 // only non-const convertible
@@ -28,8 +28,8 @@ struct IntTypeNC {
 
   constexpr bool operator==(const IntType& rhs) const { return val == rhs.val; }
   constexpr operator int() noexcept { return val; }
-  constexpr operator unsigned() { return val; }
-  constexpr operator char() noexcept { return val; }
+  constexpr operator unsigned() { return static_cast<unsigned>(val); }
+  constexpr operator char() noexcept { return static_cast<char>(val); }
 };
 
 // weird configurability of convertibility to int
diff --git a/libcxx/test/std/numerics/rand/rand.device/ctor.pass.cpp b/libcxx/test/std/numerics/rand/rand.device/ctor.pass.cpp
index a2d46ab..796ab41 100644
--- a/libcxx/test/std/numerics/rand/rand.device/ctor.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.device/ctor.pass.cpp
@@ -61,6 +61,7 @@ void check_random_device_invalid(const std::string &token) {
 int main(int, char**) {
   {
     std::random_device r;
+    (void)r;
   }
   // Check the validity of various tokens
   {
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/equal.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/equal.pass.cpp
index 4f00bd7..fc99df4 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/equal.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/equal.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) == v[j]) == expected);
       assert((v[i] == ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) == v[j]) == expected);
         assert((v[i] == std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() == abc0def) == false);
   assert((abc0def == abc.data()) == false);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) == abc0def) == false);
     assert((abc0def == std::basic_string<CharT, Traits>(abc)) == false);
   }
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/greater.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/greater.pass.cpp
index b965c15..fd3a438 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/greater.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/greater.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) > v[j]) == expected);
       assert((v[i] > ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) > v[j]) == expected);
         assert((v[i] > std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() > abc0def) == false);
   assert((abc0def > abc.data()) == true);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) > abc0def) == false);
     assert((abc0def > std::basic_string<CharT, Traits>(abc)) == true);
   }
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/greater_equal.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/greater_equal.pass.cpp
index 435e7db..0d9081e 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/greater_equal.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/greater_equal.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) >= v[j]) == expected);
       assert((v[i] >= ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) >= v[j]) == expected);
         assert((v[i] >= std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() >= abc0def) == false);
   assert((abc0def >= abc.data()) == true);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) >= abc0def) == false);
     assert((abc0def >= std::basic_string<CharT, Traits>(abc)) == true);
   }
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/less.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/less.pass.cpp
index 7461b05..bb61b1d 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/less.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/less.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) < v[j]) == expected);
       assert((v[i] < ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) < v[j]) == expected);
         assert((v[i] < std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() < abc0def) == true);
   assert((abc0def < abc.data()) == false);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) < abc0def) == true);
     assert((abc0def < std::basic_string<CharT, Traits>(abc)) == false);
   }
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/less_equal.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/less_equal.pass.cpp
index 3192db0..d91e112 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/less_equal.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/less_equal.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) <= v[j]) == expected);
       assert((v[i] <= ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) <= v[j]) == expected);
         assert((v[i] <= std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() <= abc0def) == true);
   assert((abc0def <= abc.data()) == false);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) <= abc0def) == true);
     assert((abc0def <= std::basic_string<CharT, Traits>(abc)) == false);
   }
diff --git a/libcxx/test/std/strings/string.view/string.view.comparison/not_equal.pass.cpp b/libcxx/test/std/strings/string.view/string.view.comparison/not_equal.pass.cpp
index 0082a56..a4c8be9 100644
--- a/libcxx/test/std/strings/string.view/string.view.comparison/not_equal.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.comparison/not_equal.pass.cpp
@@ -51,7 +51,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
       assert((ConvertibleTo<SV>(v[i]) != v[j]) == expected);
       assert((v[i] != ConvertibleTo<SV>(v[j])) == expected);
 
-      if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+      if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
         assert((std::basic_string<CharT, Traits>(v[i]) != v[j]) == expected);
         assert((v[i] != std::basic_string<CharT, Traits>(v[j])) == expected);
       }
@@ -72,7 +72,7 @@ TEST_CONSTEXPR_CXX14 bool test() {
   assert((abc.data() != abc0def) == true);
   assert((abc0def != abc.data()) == true);
 
-  if (!TEST_IS_CONSTANT_EVALUATED || TEST_STD_VER >= 20) {
+  if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
     assert((std::basic_string<CharT, Traits>(abc) != abc0def) == true);
     assert((abc0def != std::basic_string<CharT, Traits>(abc)) == true);
   }
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.scoped/mutex.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.scoped/mutex.pass.cpp
index 48a96f9..f953fa4 100644
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.scoped/mutex.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.scoped/mutex.pass.cpp
@@ -66,6 +66,7 @@ int main(int, char**)
     {
         using LG = std::scoped_lock<>;
         LG lg;
+        (void)lg;
     }
     {
         using LG = std::scoped_lock<TestMutex>;
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/default.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/default.pass.cpp
index 91320a5..5504645 100644
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/default.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/default.pass.cpp
@@ -22,6 +22,7 @@
 int main(int, char**)
 {
     std::shared_mutex m;
+    (void)m;
 
-  return 0;
+    return 0;
 }
diff --git a/libcxx/test/support/test_macros.h b/libcxx/test/support/test_macros.h
index f3c6d80..02678d9 100644
--- a/libcxx/test/support/test_macros.h
+++ b/libcxx/test/support/test_macros.h
@@ -151,6 +151,18 @@
 # define TEST_IS_CONSTANT_EVALUATED false
 #endif
 
+#if TEST_STD_VER >= 23
+#  define TEST_STD_AT_LEAST_23_OR_RUNTIME_EVALUATED true
+#else
+#  define TEST_STD_AT_LEAST_23_OR_RUNTIME_EVALUATED (!TEST_IS_CONSTANT_EVALUATED)
+#endif
+
+#if TEST_STD_VER >= 20
+#  define TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED true
+#else
+#  define TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED (!TEST_IS_CONSTANT_EVALUATED)
+#endif
+
 #if TEST_STD_VER >= 14
 # define TEST_CONSTEXPR_CXX14 constexpr
 #else