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From:	"Don Ward" <don2387ward AT sprynet DOT com>
To:	<cygwin AT cygwin DOT com>
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Subject:	Re: gcc4: throwing exception from signal handler
Date:	Thu, 8 Jul 2010 10:08:30 -0400
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Václav Haismam wrote:

> On Thu, 8 Jul 2010 09:01:41 -0400, "Don Ward" wrote:
>> I would like to be able to catch certain signals (SIGSEGV and SIGSYS)
> and
>> throw a C++ exception (to be caught in a try/catch construct).  As a
>> simple
>> example:
>>[...]
>> Am I misunderstanding how this should work or doing something wrong?  Or
>> is
>> this a problem with Cygwin or gcc?
> I do not think that handling SIGSEGV with an exception is a good idea.

I agree, in general.

> Unless you get SIGSEGV as a result of some well thought through memory
> management games

But that is what I am doing.  I also want to catch SIGSYS to determine 
whether shmat() is available when we don't know in advance whether cygserver 
is running.  In either case, if the signal is generated I want to catch it 
and try something else.  In these contexts I want to treat  SIGSEGV and 
SIGSYS as non-fatal error returns.

. . .
> I am not sure but I do not think that throwing exceptions from signal
> handlers is generally supported.

It appears that is what the -fnon-call-exceptions is for.  From the 
gcc-4.3.5 manual:

"-fnon-call-exceptions:  Generate code that allows trapping instructions to 
throw exceptions. Note that this requires platform-specific runtime support 
that does not exist everywhere."

I guess one question is whether the runtime support exists in Cygwin 1.7 
with gcc 4.3.4.

-- Don W.


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