Date: Sun, 2 May 1999 03:43:03 +1000 From: Bruce Evans <bde@zeta.org.au> To: cracauer@cons.org, freebsd-bugs@FreeBSD.ORG, steve@FreeBSD.ORG Subject: Re: kern/2142: FP mask not saved for signal handlers Message-ID: <199905011743.DAA03750@godzilla.zeta.org.au>
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>Synopsis: FP mask not saved for signal handlers
>
>State-Changed-From-To: suspended->closed
>State-Changed-By: steve
>State-Changed-When: Sat May 1 08:22:00 PDT 1999
>State-Changed-Why:
>kris@freebsd.org noticed this was 'suspended' and not in the 'closed' state
>as suggested in the audit trail. Attempting to fix it now. The original
>message from Martin was as follows:
>
>Closing my own old bug report, submitted back when I didn't know what
>is allowed to do in an ANSI C signal handler.
You are allowed to do silly things like:
#include <signal.h>
volatile sig_atomic_t foo;
void
handler(int signo)
{
volatile double x = 1, y = 3, z = 1.0 / 3.0;
foo = (y * z == x);
}
This does floating point computations in a signal handler and doesn't
have any side effects except the one permitted by ANSI (assigning a value
to an object declared as volatile_sig_atomic_t). The volatile doubles
just prevent some of the floating point computations being optimised away.
This shows that the FP state needs to be preserved by signal handlers.
Bruce
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