Enable <cassert> by removing -DNDEBUG when running the tests.

In non-debug builds CMake automatically adds -DNDEBUG, this means
that uses of `assert` in the tests are disabled for non-debug builds.
Obviously we want these tests to run, regardless of configuration.

This patch strips -DNDEBUG during non-debug builds and adds
-UNDEBUG just to be sure.

test/CMakeLists.txt

@@ -2,6 +2,25 @@
 
 find_package(Threads REQUIRED)
 
+# NOTE: Some tests use `<cassert>` to perform the test. Therefore we must
+# strip -DNDEBUG from the default CMake flags in DEBUG mode.
+string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
+  add_definitions( -UNDEBUG )
+  add_definitions(-DTEST_BENCHMARK_LIBRARY_HAS_NO_ASSERTIONS)
+  # Also remove /D NDEBUG to avoid MSVC warnings about conflicting defines.
+  foreach (flags_var_to_scrub
+      CMAKE_CXX_FLAGS_RELEASE
+      CMAKE_CXX_FLAGS_RELWITHDEBINFO
+      CMAKE_CXX_FLAGS_MINSIZEREL
+      CMAKE_C_FLAGS_RELEASE
+      CMAKE_C_FLAGS_RELWITHDEBINFO
+      CMAKE_C_FLAGS_MINSIZEREL)
+    string (REGEX REPLACE "(^| )[/-]D *NDEBUG($| )" " "
+      "${flags_var_to_scrub}" "${${flags_var_to_scrub}}")
+  endforeach()
+endif()
+
 # NOTE: These flags must be added after find_package(Threads REQUIRED) otherwise
 # they will break the configuration check.
 if (DEFINED BENCHMARK_CXX_LINKER_FLAGS)

test/diagnostics_test.cc

@@ -26,7 +26,7 @@ void TestHandler() {
 }
 
 void try_invalid_pause_resume(benchmark::State& state) {
-#if !defined(NDEBUG) && !defined(TEST_HAS_NO_EXCEPTIONS)
+#if !defined(TEST_BENCHMARK_LIBRARY_HAS_NO_ASSERTIONS) && !defined(TEST_HAS_NO_EXCEPTIONS)
   try {
     state.PauseTiming();
     std::abort();