On Jan 29, 2007, "Manuel López-Ibáñez" <[EMAIL PROTECTED]> wrote:
> * You can add a return 0 or an exit(1) at the end of the function or > in a default label. Since in your case the code is unreachable, the > optimiser may remove it or it will never be executed. But this would generate additional code for no useful purpose. See Ralf Baechle's posting with Subject: False ‘noreturn’ function does return warnings. /me thinks it would make sense for us to add a __builtin_unreachable() that would indicate to GCC that no further action is needed from that point on. A command-line flag could then tell whether GCC should generate abort() for such cases, or take a more general "undefined behavior" approach without generating additional code to that end. Meanwhile, there's __builtin_trap() already, and Ralf might use that even to remove the asm volatile, and Paweł could use it in a default: label. It's still worse than a __builtin_assume(e == X || e == Y), but it's probably much simpler to implement. But then, __builtin_unreachable() might very well be implemented as __builtin_assume(0). -- Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/ FSF Latin America Board Member http://www.fsfla.org/ Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org} Free Software Evangelist [EMAIL PROTECTED], gnu.org}
