tests/libcxx: Test aligned allocation with C++ new operator

Make sure the underlying allocation system can support an allocation
request generated by the new operator which has stricter alignment
requirements than the default. For G++, this ends up using the 'memalign'
function which is not part of any C standard.

Signed-off-by: Keith Packard <keithp@keithp.com>

Author: keith-packard

tests/lib/cpp/libcxx/prj.conf

@@ -2,4 +2,5 @@ CONFIG_CPP=y
 CONFIG_STD_CPP17=y
 CONFIG_ZTEST=y
 CONFIG_ZTEST_STACK_SIZE=5120
+CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=32768
 CONFIG_ZTEST_NEW_API=y

tests/lib/cpp/libcxx/src/main.cpp

@@ -9,6 +9,7 @@
 #include <memory>
 #include <vector>
 #include <zephyr/ztest.h>
+#include <zephyr/kernel.h>
 
 BUILD_ASSERT(__cplusplus == 201703);
 
@@ -95,6 +96,17 @@ ZTEST(libcxx_tests, test_exception)
 }
 #endif
 
+struct ThreadStack
+{
+	K_KERNEL_STACK_MEMBER(threadStack, 1024) {};
+};
+
+ZTEST(libcxx_tests, test_new_aligned)
+{
+	auto test_aligned = std::make_unique<ThreadStack>();
+	zassert_not_null(test_aligned, "aligned allocation failed");
+}
+
 static void *libcxx_tests_setup(void)
 {
 	TC_PRINT("version %u\n", (uint32_t)__cplusplus);