Hi,
the C11 standard provides the following example for variable-length arrays
and pointer arithmetics (see §6.5.6:10):
int main() {
int n = 4, m = 3;
int a[n][m];
int(*p)[m] = a;
assert(p == &a[0]);
p += 1;
assert(p == &a[1]);
(*p)[2] = 99;
assert(a[1][2] == 99);
n = p - a;
assert(n == 1);
}
When compiling the program with Clang 3.9, I get the following warning:
warning: subtraction of pointers to type 'int [m]' of zero size has
undefined behavior [-Wpointer-arith]
This is confusing (and probably a bug), since m is not zero and both
pointers refer to the same object. If I define a as int a[n][3] the warning
no longer appears.
- Manuel
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