do not use special gcc feature

include/enet.h

@@ -1148,7 +1148,7 @@ extern "C" {
     #define ENET_ATOMIC_READ(variable) enet_at_atomic_read((char *)(variable), ENET_ATOMIC_SIZEOF(variable))
     #define ENET_ATOMIC_WRITE(variable, new_val)                                                            \
         enet_at_atomic_write((char *)(variable), (int64_t)(new_val), ENET_ATOMIC_SIZEOF(variable))
-    #define ENET_ATOMIC_CAS(variable, old_value, new_val)                                                   \
+    #define ENET_ATOMIC_CAS(variable, old_value, new_val, assign)                                           \
         enet_at_atomic_cas((char *)(variable), (int64_t)(new_val), (int64_t)(old_value),                    \
                       ENET_ATOMIC_SIZEOF(variable))
     #define ENET_ATOMIC_INC(variable) enet_at_atomic_inc((char *)(variable), 1, ENET_ATOMIC_SIZEOF(variable))
@@ -1185,13 +1185,13 @@ extern "C" {
            potentially lost data. Replace the code with the equivalent non-sync code. */
         #ifdef __clang_analyzer__
 
-        #define ENET_ATOMIC_CAS(ptr, old_value, new_value)                                                      \
+        #define ENET_ATOMIC_CAS(ptr, old_value, new_value, assign)                                         \
             ({                                                                                             \
-                typeof(*(ptr)) ENET_ATOMIC_CAS_old_actual_ = (*(ptr));                                          \
+                typeof(*(ptr)) ENET_ATOMIC_CAS_old_actual_ = (*(ptr));                                     \
                 if (ATOMIC_CAS_old_actual_ == (old_value)) {                                               \
                     *(ptr) = new_value;                                                                    \
                 }                                                                                          \
-                ENET_ATOMIC_CAS_old_actual_;                                                                    \
+                ENET_ATOMIC_CAS_old_actual_;                                                               \
             })
 
         #else
@@ -1202,13 +1202,12 @@ extern "C" {
 
            TODO We should return bool here instead of the old value to avoid the ABA
            problem. */
-        #define ENET_ATOMIC_CAS(ptr, old_value, new_value)                                                      \
-            ({                                                                                             \
-                typeof(*(ptr)) ENET_ATOMIC_CAS_expected_ = (old_value);                                         \
-                __atomic_compare_exchange_n((ptr), &ENET_ATOMIC_CAS_expected_, (new_value), false,              \
-                                            __ATOMIC_ACQ_REL, __ATOMIC_ACQUIRE);                           \
-                ENET_ATOMIC_CAS_expected_;                                                                      \
-            })
+        #define ENET_ATOMIC_CAS(ptr, old_value, new_value, assign)                                         \
+            0;                                                                                             \
+            typeof(*(ptr)) ENET_ATOMIC_CAS_expected_ = (old_value);                                        \
+            __atomic_compare_exchange_n((ptr), &ENET_ATOMIC_CAS_expected_, (new_value), false,             \
+                                        __ATOMIC_ACQ_REL, __ATOMIC_ACQUIRE);                               \
+            assign = ENET_ATOMIC_CAS_expected_;                                                                 
 
         #endif /* __clang_analyzer__ */
 
@@ -1222,7 +1221,7 @@ extern "C" {
         #define ENET_ATOMIC_READ(variable) __sync_fetch_and_add(variable, 0)
         #define ENET_ATOMIC_WRITE(variable, new_val)                                                            \
             (void) __sync_val_compare_and_swap((variable), *(variable), (new_val))
-        #define ENET_ATOMIC_CAS(variable, old_value, new_val)                                                   \
+        #define ENET_ATOMIC_CAS(variable, old_value, new_val, assign)                                           \
             __sync_val_compare_and_swap((variable), (old_value), (new_val))
         #define ENET_ATOMIC_INC(variable) __sync_fetch_and_add((variable), 1)
         #define ENET_ATOMIC_DEC(variable) __sync_fetch_and_sub((variable), 1)
@@ -5004,7 +5003,7 @@ extern "C" {
             // Set the value of the start_time_ns, such that the first timestamp
             // is at 1ms. This ensures 0 remains a special value.
             uint64_t want_value = current_time_ns - 1 * ns_in_ms;
-            uint64_t old_value = ENET_ATOMIC_CAS(&start_time_ns, 0, want_value);
+            uint64_t old_value = ENET_ATOMIC_CAS(&start_time_ns, 0, want_value, old_value);
             offset_ns = old_value == 0 ? want_value : old_value;
         }