gcc7.2: argument range exceeds maximum object size 9..7 [-Werror=alloc-size-larger-than=]

Question

The program contains code like follows:

int size;
...
int *pi = (int*)calloc(size, sizeof(int));
...

Here is the error message when compiled with gcc7.2：

error: argument 1 range [18446744071562067968, 18446744073709551615] exceeds maximum object size 9223372036854775807 [-Werror=alloc-size-larger-than=]

When I change
int *pi = (int*)calloc(size, sizeof(int)); to
int *pi = (int*)calloc((unsigned int)size, sizeof(int));

The error disappeared.

However, in the program, there are many malloc and calloc used like my original version.

Why there is only one error detected by gcc?

Answer 1

I recently had the same problem on my GCC 9.1 build, and I found this discussion on the GCC Bugzilla:

https://gcc.gnu.org/bugzilla//show_bug.cgi?id=85783

As mentioned in the link discussion, I was able to suppress the warning by checking the size parameter against PTRDIFF_MAX.