void error(const char* msg);
int successor(int a) {
if (a + 1 < a) error("Integer overflow!");
return a + 1;
}
and says the if is compiled away at -O3, does any one know if it remains at any lower optimization level? I know some of the more aggressive optimizations intentionally ignore some checks, I don't know if that applies here. I found the -O3 odd for trying to help make his point, unless it doesn't work at -O2.
It's optimized out on both gcc and clang on -O1 and above. -O3 is presumably just what the author defaults to for enabling optimizations (I also write -O3 everywhere by default).
Comments
In the bit where he shows
and says the if is compiled away at -O3, does any one know if it remains at any lower optimization level? I know some of the more aggressive optimizations intentionally ignore some checks, I don't know if that applies here. I found the -O3 odd for trying to help make his point, unless it doesn't work at -O2.It's optimized out on both gcc and clang on -O1 and above. -O3 is presumably just what the author defaults to for enabling optimizations (I also write -O3 everywhere by default).