[libcxx] Add DoNotOptimize function call to libcxx tests where appropriate

It has been seen, at high levels of optimizations, issues with comparing the
pointer values in some libcxx tests attaining to the assert comparing the pointer
of a global variable to that of one created locally within the test. These tests
follow the same logic as others that utilize the `DoNotOptimize` function, however
these tests do not.

To ensure the correct behaviour at high levels of optimization, these tests now utilize
the function when building the tests. This allows for the correct behaviour to be
observed when running the tests.

Author: Stylie777

libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.array/new.size_align.replace.pass.cpp

@@ -48,11 +48,12 @@ int main(int, char**) {
     // Test with an overaligned type
     {
         new_called = delete_called = 0;
-        OverAligned* x = new OverAligned[3];
+        OverAligned* dummy_data_block = new OverAligned[3];
+        OverAligned* x             = DoNotOptimize(dummy_data_block);
         assert(static_cast<void*>(x) == DummyData);
         assert(new_called == 1);
 
-        delete[] x;
+        delete[] dummy_data_block;
         assert(delete_called == 1);
     }
 

libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/new.size_align.replace.pass.cpp

@@ -48,11 +48,12 @@ int main(int, char**) {
     // Test with an overaligned type
     {
         new_called = delete_called = 0;
-        OverAligned* x = new OverAligned;
+        OverAligned* dummy_data_block = new OverAligned;
+        OverAligned* x             = DoNotOptimize(dummy_data_block);
         assert(static_cast<void*>(x) == DummyData);
         assert(new_called == 1);
 
-        delete x;
+        delete dummy_data_block;
         assert(delete_called == 1);
     }
 

libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/new.size_align_nothrow.replace.pass.cpp

@@ -47,11 +47,12 @@ int main(int, char**) {
     // Test with an overaligned type
     {
         new_nothrow_called = delete_called = 0;
-        OverAligned* x = new (std::nothrow) OverAligned;
+        OverAligned* dummy_data_block = new (std::nothrow) OverAligned;
+        OverAligned* x                     = DoNotOptimize(dummy_data_block);
         assert(static_cast<void*>(x) == DummyData);
         ASSERT_WITH_OPERATOR_NEW_FALLBACKS(new_nothrow_called == 1);
 
-        delete x;
+        delete dummy_data_block;
         ASSERT_WITH_OPERATOR_NEW_FALLBACKS(delete_called == 1);
     }