os: add alloca func

include/os/os.h

@@ -52,6 +52,7 @@ extern "C" {
 #endif
 #else
 
+#include <malloc.h>
 #include <time.h>
 #ifndef TD_USE_WINSOCK
 #include <winsock2.h>

include/os/osMath.h

@@ -25,11 +25,10 @@ extern "C" {
 
 #define TSWAP(a, b)                              \
   do {                                           \
-    char *__tmp = taosMemoryMalloc(sizeof(a));   \
+    char *__tmp = alloca(sizeof(a));             \
     memcpy(__tmp, &(a), sizeof(a));              \
     memcpy(&(a), &(b), sizeof(a));               \
     memcpy(&(b), __tmp, sizeof(a));              \
-    taosMemoryFree(__tmp);                       \
   } while (0)
 
 #ifdef WINDOWS