gcc 3.4 Compiler warning

[Christian Ehrlicher]

Hello

I got following warning where I don't expect.
"null argument where non-null required (arg 2)"

I tried to simplify the code so it looks a little bit senseless ... 
normally this is in a bigger macro where I won't check if size is 0

------------------8<------------------------------------------------
#include <string.h>

#define MY_RET_DEF_SIZ(typ) ( my_ret[typ] )

int main(int argc, char **argv) {
     char * tmp1 = "1234567890";
     static char my_ret[] = { 0, 1, 2, 4, 4, 8, 16, 32, 80, 0 };

     memmove(tmp1,0,MY_RET_DEF_SIZ(0));

     return 0;
}

------------------8<------------------------------------------------

It works because MY_RET_DEF_SIZ return 0 and so I think the warning 
isn't usefull there.
What do you think?

Thx
Christian