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Groups > comp.lang.c > #24091

Re: signal() anomaly

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On Tue, 31 Jul 2012 16:35:41 -0400, Eric Sosman wrote:

> On 7/31/2012 4:13 PM, hip cat wrote:
>> What up
>>
>> I've used signal to set SIGSEGV to SIG_IGN. But when I later dereference
>> a null pointer my program still crashes out with segfault SIGSEGV. What
>> gives?
> 
>      Did you check that the signal() call succeeded?  That is,
> was the returned value SIG_ERR or something else?
> 
>      On POSIX systems, ignoring SIGSEGV produces undefined behavior.

POSIX is a bit more specific than that.  But regardless...

> The C Standard isn't quite so clear to me: It's U.B. if a signal
> handler for SIGSEGV returns (7.14.1.1p3), but SIG_IGN is not a
> "signal handler" under the definition of 7.14.1.1p2.

...the C standard doesn't need to be any more explicit on this matter.
The behaviour is undefined because the program has dereferenced an
invalid (null) pointer.  The handling of SIGSEGV is irrelevant.

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signal() anomaly hip cat <nospam@nospam.com> - 2012-07-31 20:13 +0000
  Re: signal() anomaly Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-31 16:35 -0400
    Re: signal() anomaly hip cat <nospam@nospam.com> - 2012-08-01 18:59 +0000
    Re: signal() anomaly Nick Bowler <nbowler@draconx.ca> - 2012-08-01 20:14 +0000
  Re: signal() anomaly falk@rahul.net (Edward A. Falk) - 2012-07-31 22:12 +0000
    Re: signal() anomaly hip cat <nospam@nospam.com> - 2012-08-01 18:58 +0000
      Re: signal() anomaly James Kuyper <jameskuyper@verizon.net> - 2012-08-01 15:33 -0400
        Re: signal() anomaly hip cat <nospam@nospam.com> - 2012-08-01 20:47 +0000
          Re: signal() anomaly Paul <nospam@needed.com> - 2012-08-01 17:34 -0400
            Re: signal() anomaly Johann Klammer <klammerj@NOSPAM.a1.net> - 2012-08-02 06:34 +0200
              Re: signal() anomaly Paul <nospam@needed.com> - 2012-08-02 07:10 -0400
          Re: signal() anomaly Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-01 18:07 -0400
            Re: signal() anomaly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-02 00:15 +0100
              Re: signal() anomaly Nick Bowler <nbowler@draconx.ca> - 2012-08-02 00:05 +0000
                Re: signal() anomaly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-02 02:47 +0100
          Re: signal() anomaly James Kuyper <jameskuyper@verizon.net> - 2012-08-01 18:13 -0400
          Re: signal() anomaly James Kuyper <jameskuyper@verizon.net> - 2012-08-01 18:14 -0400
          Re: signal() anomaly Nobody <nobody@nowhere.com> - 2012-08-02 12:52 +0100
      Re: signal() anomaly Angel <angel+news@spamcop.net> - 2012-08-01 19:41 +0000
      Re: signal() anomaly Kenneth Brody <kenbrody@spamcop.net> - 2012-08-01 16:16 -0400
      Re: signal() anomaly Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-01 16:33 -0400
      Re: signal() anomaly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-02 00:22 +0100
      Re: signal() anomaly Stephen Sprunk <stephen@sprunk.org> - 2012-08-02 00:55 -0500
        Re: signal() anomaly Ike Naar <ike@sverige.freeshell.org> - 2012-08-02 07:01 +0000
      Re: signal() anomaly Öö Tiib <ootiib@hot.ee> - 2012-09-08 20:53 -0700
  Re: signal() anomaly Nobody <nobody@nowhere.com> - 2012-08-01 18:06 +0100
    Re: signal() anomaly Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 13:44 -0700
  Re: signal() anomaly Kleuske <kleuske@nowhere.net> - 2012-08-02 20:52 +0000

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