Re: [PATCH 30/30] tools/testing/vma: output compared expression on ASSERT_[EQ, NE]()

On Mon, Jun 29, 2026 at 01:23:41PM +0100, Lorenzo Stoakes wrote:
> -#define ASSERT_TRUE(_expr)						\
> -	do {								\
> -		if (!(_expr)) {						\
> -			fprintf(stderr,					\
> -				"Assert FAILED at %s:%d:%s(): %s is FALSE.\n", \
> -				__FILE__, __LINE__, __FUNCTION__, #_expr); \
> -			return false;					\
> -		}							\
> +#define __ASSERT_TRUE(_expr, _fmt, ...)					   \
> +	do {								   \
> +		if (!(_expr)) {						   \
> +			fprintf(stderr,					   \
> +				"Assert FAILED at %s:%d:%s(): %s is FALSE" \
> +				_fmt ".\n",				   \
> +				__FILE__, __LINE__, __FUNCTION__, #_expr   \
> +				__VA_OPT__(,) __VA_ARGS__);		   \
> +			return false;					   \
> +		}							   \
>  	} while (0)
> 
> +#define __TO_SCALAR(x)	((unsigned long long)(uintptr_t)(x))
> +
> +#define ASSERT_TRUE(_expr) __ASSERT_TRUE(_expr, "")

Mmmmm... macro madness.... I don't think this is what you want.

I think you end up double-running the expression in the failure branch.

  ASSERT_EQ(cleanup_mm(&mm, &vmi), 2)

run through the preprocessor expands to:

  do {
      if (!( (cleanup_mm(&mm, &vmi)) == (2) )) {
              **** first run ****

          fprintf(stderr,
              "Assert FAILED at %s:%d:%s(): %s is FALSE" " (0x%llx != 0x%llx)" ".\n",
              "merge.c", 645, __FUNCTION__,
              "(cleanup_mm(&mm, &vmi)) == (2)",
              ((unsigned long long)(uintptr_t)(cleanup_mm(&mm, &vmi))),
                                               **** second run ****

              ((unsigned long long)(uintptr_t)(2)));
          return false;
      }
  } while (0);


A bunch of existing ASSERT callers mutate state, so there's no guarantee
the printed value matches teh actual test value.

I think you want something like:

#define ASSERT_EQ(_val1, _val2) do {	\
	__auto_type _v1 = (_val1);	\
	__auto_type _v2 = (_val2);	\
	__ASSERT_TRUE(_v1 == _v2, " (0x%llx != 0x%llx)",	\
		__TO_SCALAR(_v1), __TO_SCALAR(_v2));	\
} while (0)

which expands to:

  do {
      __auto_type _v1 = (cleanup_mm(&mm, &vmi));
      __auto_type _v2 = (2);
      do {
          if (!(_v1 == _v2)) {
              fprintf(stderr, "...FALSE (0x%llx != 0x%llx).\n",
                      "merge.c", 645, __FUNCTION__, "_v1 == _v2",
                      ((unsigned long long)(uintptr_t)(_v1)),
                      ((unsigned long long)(uintptr_t)(_v2)));
              return false;
          }
      } while (0);
  } while (0);

~Gregory