Signal handler for SIGSEGV.

[vashwath]

Hi all,
In my current project I am using signals for error handling. Since I
cannot show full code, I have just shown important piece of code which
is relevant.

void sigsegenv()
{
printf("\n\n ********** F D S Message ***********\n\n ");
printf("\n\n ********** S E G M E N T A T I O N F A U L T
inside F D S ***********\n\n ");
exit(-1);
}
int main(void)
{
............
...........
signal ( SIGSEGV ,sigsegenv);
...........
...........
}

I think this might give some idea about what is happening.
My signal handler is not catching SIGSEGV always. Some time it is
catching sometimes not. Please let me know what am I doing wrong

[SM Ryan]

va******@rediff mail.com wrote:

# Can I invoke longjmp in signal handler?

Your program is in a fragile state when the signal handler
is called, and it might not be possible to recover and
continue. On some systems, you can run the program in a
separate process; if it fails, it can report failure and
then exit with recovery. The caller monitors the process
and captures the result or error status.

--
SM Ryan http://www.rawbw.com/~wyrmwif/
TEMPORARILY CLOSED
BE OPENED AFTER FIRST PERIOD

[Markus.Elfring]

> Could you please tell me about restrictions on signal handlers or where

I can find more info about restrictions on signal handlers?

Please look at the list of async-signal-safe functions.
See section "2.4.3 Signal Actions" from the document " 2.4 Signal
Concepts".
http://www.opengroup.org/onlinepubs/...l#tag_02_04_03
http://en.wikipedia.org/wiki/Signal_%28computing%29

Regards,
Markus

[Flash Gordon]

Ma************@ web.de wrote:

Could you please tell me about restrictions on signal handlers or where
I can find more info about restrictions on signal handlers?

Please look at the list of async-signal-safe functions.
See section "2.4.3 Signal Actions" from the document " 2.4 Signal
Concepts".
http://www.opengroup.org/onlinepubs/...l#tag_02_04_03
http://en.wikipedia.org/wiki/Signal_%28computing%29

The above links are Posix, not C. I can't remember the OP saying that
this was only for Posix systems, and if it was then this would be the
wrong group.

A better place to look would be the C standard, a draft of the latest
version being freely available if you search for n1124.pdf.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[Markus.Elfring]

> A better place to look would be the C standard, a draft of the latest

version being freely available if you search for n1124.pdf.

http://www.open-std.org/jtc1/sc22/wg...1997/N1124.pdf

This document (ISO/IEC 9899:TC2 Committee Draft - May 6, 2005
WG14/N1124) contains the following wording.
Page 20, section "5.2.3 Signals and interrupts":
"...
Functions shall be implemented such that they may be interrupted at any
time by a signal, or may be called by a signal handler, or both, with
no alteration to earlier, but still active, invocations' control flow
(after the interruption), function return values, or objects with
automatic storage duration.
...."

Page 167, section "7.1.4 Use of library functions":
"...
The functions in the standard library are not guaranteed to be
reentrant and may modify objects with static storage duration.
....
161) Thus, a signal handler cannot, in general, call standard library
functions.
...."

There are more descriptions about signal handling in the sections 7.14
and 7.26.6. But the term "async-signal-safe function" is not used in
the specification. I suggest to look at other information sources for
better understanding of the topic "async-signal safety".
- Multithreaded Programming Guide

http://docs.sun.com/app/docs/doc/816...w#compat-ix626
http://docs.sun.com/app/docs/doc/816...view#gen-ix561

- http://serpentine.com/blog/threads-faq/signals.html

- http://en.wikipedia.org/wiki/Reentrant
http://en.wikipedia.org/wiki/SIGSEGV

Regards,
Markus