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gcc makes my day

Ben pointed out the -ftrapv feature in gcc, something I have wanted for a while.

-ftrapv

This option generates traps for signed overflow on addition, subtraction, multiplication operations.

Example:

int main()
{
     int x = 1;
     while (1) {
          x *= 2;
          printf("%u\n", x);
     }
     return 0;
}

gcc -Wall -ftrapv overflow.c -o overflow -O3 && ./overflow >/dev/null

aborted

The current implementation seems to turn these operations into function calls, which may be a bit slow. It seems like it could potentially be done inline. But it's still something that might be very useful in test-builds or in security-sensitive software.

posted Wed 2 Feb 2005 in /software/languages/C | link

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