oops, forgot the "Fixes" line. Sent a v2.
--
Nadav Har'El
n...@scylladb.com
On Wed, Jan 11, 2023 at 1:53 PM Nadav Har'El <n...@scylladb.com> wrote:
> tst-feexcept.cc checks several aspects of SIGFPE. One of the things
> we noticed in the past, and tested, is that division by *integer* zero
> also generates SIGFPE. We had a test for this using C code, but
> unfortunately C and C++ chose to make division by zero "undefined",
> and starting with Gcc 12, 1/0 started to return 0 instead of SIGFPE
> which broke this test.
>
> Changed the test to do division by zero in assembly-language, which
> still causes a SIGFPE.
>
> Signed-off-by: Nadav Har'El <n...@scylladb.com>
> ---
> tests/tst-feexcept.cc | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tests/tst-feexcept.cc b/tests/tst-feexcept.cc
> index 5d5ddc1f..403185b6 100644
> --- a/tests/tst-feexcept.cc
> +++ b/tests/tst-feexcept.cc
> @@ -78,8 +78,12 @@ int main(int argc, char **argv)
> // Test that fegetexcept() does not return a negative number
> expect(fegetexcept() >= 0, true);
>
> - // Test that *integer* division by zero generates, ironically, a
> SIGFPE
> - expect(sig_check([] { printf("%d\n", 1 / zero_i()); }, SIGFPE), true);
> + // Test that *integer* division by zero generates, ironically, a
> SIGFPE.
> + // Starting with Gcc 12, division by zero in C no longer generates a
> + // SIGFPE and just returns 0. So to check this we need to use assembly
> + // directly.
> + //expect(sig_check([] { printf("%d\n", 1 / zero_i()); }, SIGFPE),
> true);
> + expect(sig_check([] { asm("movl $1,%eax; movl $0,%ebx; movl $0, %edx;
> divl %ebx;"); }, SIGFPE), true);
>
> // While, continuing the irony, by default a floating-point division
> by
> // zero does NOT generate a SIGFPE signal, but rather inf or nan:
> --
> 2.39.0
>
>
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