Trapping Ctrl-C, how?

**Eric Sosman** · Nov 13 '05, 07:58 PM

Re: Trapping Ctrl-C, how?

Wurm wrote:[color=blue]
>
> Hi all,
>
> Got a little problem [...][/color]

.... which happens to be Question 19.38 in the comp.lang.c
Frequently Asked Questions (FAQ) list

comp.lang.c Frequently Asked Questions

http://www.eskimo.com/~scs/C-faq/top.html

--
Eric.Sosman@sun .com

**Wurm** · Nov 13 '05, 07:58 PM

Re: Trapping Ctrl-C, how?

Eric Sosman <Eric.Sosman@su n.com> wrote in message
news:3F83107C.D 1834264@sun.com ...[color=blue]
> Wurm wrote:[color=green]
> >
> > Hi all,
> >
> > Got a little problem [...][/color]
>
> ... which happens to be Question 19.38 in the comp.lang.c
> Frequently Asked Questions (FAQ) list
>
> http://www.eskimo.com/~scs/C-faq/top.html
>
> --
> Eric.Sosman@sun .com[/color]

Well son-of-a......., thanks!. Ill definetly take some time and look through
that FAQ, didnt even know it was there :)

Wurm

**E. Robert Tisdale** · Nov 13 '05, 07:58 PM

Re: Trapping Ctrl-C, how?

Eric Sosman wrote:
[color=blue]
> Wurm wrote:
>[color=green]
>>Got a little problem [...][/color]
>
> ... which happens to be Question 19.38 in the comp.lang.c
> Frequently Asked Questions (FAQ) list
>
> http://www.eskimo.com/~scs/C-faq/top.html[/color]

Excellent answer!

**CBFalconer** · Nov 13 '05, 07:58 PM

Re: Trapping Ctrl-C, how?

Wurm wrote:[color=blue]
>
> Got a little problem with a lib that I'm working on. First of all,
> the problem is that the lib that I have makes connections to
> DirectSound, and has a host of custom built sound related
> functions. Now, in the lib is a 'destroy' function which when
> called will release all instances of DirectSound that I have
> created and if that is used, then great, no problem. The
> application that uses this lib is a console application running
> on WindowsNT 4.0 sp6, and before connecting to this lib, if we
> wanted to kill the app we simply hit Ctrl+C and it dies. But
> now that its been connected to my lib, if we do a Ctrl+C instead
> of the app dissapearing it hangs and times out which
> unfortunately is unnaceptable for our usage. So to solve this, I
> either have to find a way to trap when the user hits Ctrl+C and
> call my own 'destroy' function before releasing the Ctrl+C back
> to the OS, or, have to find a way in DirectSound to configure it
> so that if the controlling app dies, the objects created are
> released automatically (this I've already looked for and cant
> find).[/color]

Most of that is OT on c.l.c. Maybe you want to find another way
of signalling the program to exit.

However if Ctrl-C causes the program to perform a normal exit
(so-called), the following STANDARD function may help. From N869.

7.20.4.2 The atexit function

Synopsis

[#1]
#include <stdlib.h>
int atexit(void (*func)(void));

Description

[#2] The atexit function registers the function pointed to
by func, to be called without arguments at normal program
termination.

Environmental limits

[#3] The implementation shall support the registration of at
least 32 functions.

Returns

[#4] The atexit function returns zero if the registration
succeeds, nonzero if it fails.

--
Chuck F (cbfalconer@yah oo.com) (cbfalconer@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

**Keith Thompson** · Nov 13 '05, 07:58 PM

Re: Trapping Ctrl-C, how?

CBFalconer <cbfalconer@yah oo.com> writes:
[...][color=blue]
> Most of that is OT on c.l.c. Maybe you want to find another way
> of signalling the program to exit.
>
> However if Ctrl-C causes the program to perform a normal exit
> (so-called), the following STANDARD function may help. From N869.
>
> 7.20.4.2 The atexit function[/color]
[...]

Ctrl-C typically causes a signal to be sent to the currently running
program. That generally doesn't result in a normal exit, so it
bypasses any atexit()-registered functions.

--
Keith Thompson (The_Other_Keit h) kst@cts.com <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://www.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"

**Richard Heathfield** · Nov 13 '05, 07:59 PM

Re: Trapping Ctrl-C, how?

CBFalconer wrote:
[color=blue]
> Most of that is OT on c.l.c. Maybe you want to find another way
> of signalling the program to exit.
>[/color]
<snip>[color=blue]
>
> [#2] The atexit function registers the function pointed to
> by func, to be called without arguments at normal program
> termination.[/color]

Does a SIGTERM signal count as "normal termination"?

Perhaps the guy just needs to read[1] up on signal().

[1] I first typed this as "reed". I think I must be getting fnetic in my old
aj.

--
Richard Heathfield : binary@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

**Dan Pop** · Nov 13 '05, 07:59 PM

Re: Trapping Ctrl-C, how?

In <3F83107C.D1834 264@sun.com> Eric Sosman <Eric.Sosman@su n.com> writes:
[color=blue]
>Wurm wrote:[color=green]
>>
>> Hi all,
>>
>> Got a little problem [...][/color]
>
>... which happens to be Question 19.38 in the comp.lang.c
>Frequently Asked Questions (FAQ) list
>
> http://www.eskimo.com/~scs/C-faq/top.html[/color]

What the FAQ doesn't say is that the implementation of SIGINT in
Windows is broken: the signal handler will be executed in a new thread,
rather than having the program execution suspended until the signal
handler returns. This has bitten more than one unsuspecting Windows
programmer...

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Dan Pop** · Nov 13 '05, 07:59 PM

Re: Trapping Ctrl-C, how?

In <bm01b6$6l2$2@h ercules.btinter net.com> Richard Heathfield <dontmail@addre ss.co.uk.invali d> writes:
[color=blue]
>CBFalconer wrote:
>[color=green]
>> Most of that is OT on c.l.c. Maybe you want to find another way
>> of signalling the program to exit.
>>[/color]
><snip>[color=green]
>>
>> [#2] The atexit function registers the function pointed to
>> by func, to be called without arguments at normal program
>> termination.[/color]
>
>Does a SIGTERM signal count as "normal termination"?[/color]

How can you send a SIGTERM signal to a Windows program? CTRL-C is
supposed to send a SIGINT.

Anyway, the simple delivery of any of them does not cause normal program
termination: they're merely asking the program to terminate. It's up to
the program to decide what to do.
[color=blue]
>Perhaps the guy just needs to read[1] up on signal().[/color]

Preferably, from the Windows documentation, for a reason mentioned
in another post.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**CBFalconer** · Nov 13 '05, 08:00 PM

Re: Trapping Ctrl-C, how?

Dan Pop wrote:[color=blue]
> Eric Sosman <Eric.Sosman@su n.com> writes:[color=green]
> >Wurm wrote:[color=darkred]
> >>
> >> Got a little problem [...][/color]
> >
> > ... which happens to be Question 19.38 in the comp.lang.c
> > Frequently Asked Questions (FAQ) list
> >
> > http://www.eskimo.com/~scs/C-faq/top.html[/color]
>
> What the FAQ doesn't say is that the implementation of SIGINT in
> Windows is broken: the signal handler will be executed in a new
> thread, rather than having the program execution suspended until
> the signal handler returns. This has bitten more than one
> unsuspecting Windows programmer...[/color]

Which, I assume, means that the handler must set a "global" flag,
and that the program must check that at predetermined places to
handle such a CTL-C operation.

--
Chuck F (cbfalconer@yah oo.com) (cbfalconer@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

**Richard Heathfield** · Nov 13 '05, 08:00 PM

Re: Trapping Ctrl-C, how?

Dan Pop wrote:[color=blue]
> Richard Heathfield writes:[color=green]
>>CBFalconer wrote:
>>[/color][/color]
<snip>[color=blue][color=green][color=darkred]
>>> [#2] The atexit function registers the function pointed to
>>> by func, to be called without arguments at normal program
>>> termination.[/color]
>>
>>Does a SIGTERM signal count as "normal termination"?[/color]
>
> How can you send a SIGTERM signal to a Windows program? CTRL-C is
> supposed to send a SIGINT.[/color]

Yes, you're right. Two likely candidates to choose from, so obviously I
chose the wrong one.

--
Richard Heathfield : binary@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

**Dan Pop** · Nov 13 '05, 08:00 PM

Re: Trapping Ctrl-C, how?

In <3F843F0B.FDBD0 F7@yahoo.com> CBFalconer <cbfalconer@yah oo.com> writes:
[color=blue]
>Dan Pop wrote:[color=green]
>> Eric Sosman <Eric.Sosman@su n.com> writes:[color=darkred]
>> >Wurm wrote:
>> >>
>> >> Got a little problem [...]
>> >
>> > ... which happens to be Question 19.38 in the comp.lang.c
>> > Frequently Asked Questions (FAQ) list
>> >
>> > http://www.eskimo.com/~scs/C-faq/top.html[/color]
>>
>> What the FAQ doesn't say is that the implementation of SIGINT in
>> Windows is broken: the signal handler will be executed in a new
>> thread, rather than having the program execution suspended until
>> the signal handler returns. This has bitten more than one
>> unsuspecting Windows programmer...[/color]
>
>Which, I assume, means that the handler must set a "global" flag,
>and that the program must check that at predetermined places to
>handle such a CTL-C operation.[/color]

A strategy that doesn't work very well if the program is stuck into an
input call that never returns, for one reason or another...

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Wurm** · Nov 13 '05, 08:01 PM

Re: Trapping Ctrl-C, how?

Thanks all, the signal() calls did the trick!. Ill definetly read up on that
FAQ

"Wurm" <a@b.c> wrote in message news:blv2ih$ko7 $1@dns3.cae.ca. ..[color=blue]
> Hi all,
>
> Got a little problem with a lib that I'm working on. First of all, the
> problem is that the lib that I have makes connections to DirectSound, and
> has a host of custom built sound related functions. Now, in the lib is a
> 'destroy' function which when called will release all instances of
> DirectSound that I have created and if that is used, then great, no[/color]
problem.[color=blue]
> The application that uses this lib is a console application running on
> WindowsNT 4.0 sp6, and before connecting to this lib, if we wanted to kill
> the app we simply hit Ctrl+C and it dies. But now that its been connected[/color]
to[color=blue]
> my lib, if we do a Ctrl+C instead of the app dissapearing it hangs and[/color]
times[color=blue]
> out which unfortunately is unnaceptable for our usage. So to solve this, I
> either have to find a way to trap when the user hits Ctrl+C and call my[/color]
own[color=blue]
> 'destroy' function before releasing the Ctrl+C back to the OS, or, have to
> find a way in DirectSound to configure it so that if the controlling app
> dies, the objects created are released automatically (this I've already
> looked for and cant find).
>
> So.... thanks for reading this far!, does anyone know how to do this?.[/color]
Bear[color=blue]
> in mind, I have no control over the creation of the window (I found a[/color]
group[color=blue]
> of functions which seem that they would do the job, WindowProc and friends
> but they need to be fully setup at the window creation which I cant do).[/color]
Ive[color=blue]
> tried the SetWindowsHookE x family of functions but for one reason or[/color]
another[color=blue]
> I cannot get any test hooks to trigger at all and I was told that they may
> not function properly with console applications.
>
> Any input at all would be greatly appreciated, post here or if you prefer
> mail me directly at: pforan AT cae DOT com
>
> TIA!
>
> Phil
>
>[/color]

Trapping Ctrl-C, how?

Trapping Ctrl-C, how?

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