Hi, With the addition of the following patch http://gcc.gnu.org/ml/gcc-patches/2008-04/msg00565.html gcc now complains about the following code snippet, saying... warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 char const x[] = "deadbeef"; int main (void) { for (char const *ptr = x; ptr < x + 4; ptr++) putc (*ptr, stdout); return 0; } However, it does not complain if the code is changed as follows: char const *x = "deadbeef"; int main (void) { for (char const *ptr = x; ptr < x + 4; ptr++) putc (*ptr, stdout); return 0; } The description included in the patch states: This option also allows the compiler to assume strict pointer semantics: given a pointer to an object, if adding an offset to that pointer does not produce a pointer to the same object, the addition is undefined. This permits the compiler to conclude that @code{p + i > p} is always true for a pointer @code{p} and integer @code{i}. This assumption is only valid if pointer wraparound is undefined, as the expression is false if @code{p + i} overflows. In the first snippet ptr never points outside x[], so the compiler shouldn't warn. What am I missing here? Cheers, - Udo
