[Bug middle-end/54848] New: -ftrapv doesn't work when assigning to an integer with smaller size

[mikulas at artax dot karlin.mff.cuni.cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54848



             Bug #: 54848

           Summary: -ftrapv doesn't work when assigning to an integer with

                    smaller size

    Classification: Unclassified

           Product: gcc

           Version: 4.7.2

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: middle-end

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: miku...@artax.karlin.mff.cuni.cz

              Host: i686-pc-linux-gnu

            Target: i686-pc-linux-gnu

             Build: i686-pc-linux-gnu





When adding, subtracting or multiplying two integers and assigning the result

to a variable with smaller size, trap on overflow doesn't happen.



See for example this program:



#include <stdio.h>



int main(void)

{

        int a = 0x70000000;

        int b = 0x50000000;

        short c = a + b;

        printf("%x\n", c);

        return 0;

}



We compile the program without optimization and with -ftrapv, so that it should

crash because of integer overflow. But the program doesn't crash. If we replace

"short" with "int", an overflow crash happens correctly.