PR comments: rework compiler flags

CMakeLists.txt

@@ -221,6 +221,11 @@ if(S2N_UNSAFE_FUZZING_MODE)
     target_compile_options(${PROJECT_NAME} PRIVATE -fsanitize-coverage=trace-pc-guard -fsanitize=address,undefined,leak -fuse-ld=gold -DS2N_ADDRESS_SANITIZER=1)
 endif()
 
+if(TSAN)
+    target_compile_options(${PROJECT_NAME} PUBLIC -fsanitize=thread -DS2N_THREAD_SANITIZER=1)
+    target_link_options(${PROJECT_NAME} PUBLIC -fsanitize=thread)
+endif()
+
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 if (NOT $ENV{S2N_LIBCRYPTO} MATCHES "awslc")
@@ -352,13 +357,6 @@ if (NOT S2N_EXECINFO_AVAILABLE)
 endif()
 feature_probe_result(S2N_STACKTRACE ${S2N_STACKTRACE})
 
-if(TSAN)
-    target_compile_options(${PROJECT_NAME} PUBLIC -fsanitize=thread)
-    target_link_options(${PROJECT_NAME} PUBLIC -fsanitize=thread)
-    # For now, only enable real atomics for TSAN
-    feature_probe_result(S2N_ATOMIC_ENABLED ${S2N_ATOMIC_SUPPORTED})
-endif()
-
 set(S2N_KYBER512R3_AVX2_BMI2 FALSE)
 if(NOT S2N_NO_PQ_ASM)
     # Kyber Round-3 code has several different optimizations which require

utils/s2n_atomic.c

@@ -21,15 +21,15 @@
 
 S2N_RESULT s2n_atomic_init()
 {
-#if S2N_ATOMIC_ENABLED
+#if S2N_ATOMIC_SUPPORTED && S2N_THREAD_SANITIZER
     RESULT_ENSURE(__atomic_always_lock_free(sizeof(s2n_atomic_bool), NULL), S2N_ERR_ATOMIC);
 #endif
     return S2N_RESULT_OK;
 }
 
 void s2n_atomic_store(s2n_atomic_bool *var, bool val)
 {
-#if S2N_ATOMIC_ENABLED
+#if S2N_ATOMIC_SUPPORTED && S2N_THREAD_SANITIZER
     sig_atomic_t input = val;
     __atomic_store(&var->val, &input, __ATOMIC_RELAXED);
 #else
@@ -39,7 +39,7 @@ void s2n_atomic_store(s2n_atomic_bool *var, bool val)
 
 bool s2n_atomic_load(s2n_atomic_bool *var)
 {
-#if S2N_ATOMIC_ENABLED
+#if S2N_ATOMIC_SUPPORTED && S2N_THREAD_SANITIZER
     sig_atomic_t result = 0;
     __atomic_load(&var->val, &result, __ATOMIC_RELAXED);
     return result;