From:	"Andrew Crabtree" <andrewc AT rosemail DOT rose DOT hp DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Exceptions work with -fsjlj-exceptions flag. Why?
Date:	Mon, 23 Mar 1998 09:54:41 -0800
Organization:	Hewlett Packard
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To:	djgpp AT delorie DOT com
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David Vrabel wrote in message <351671d4 DOT 2800186 AT 192 DOT 168 DOT 1 DOT 250>...
>To get exception handling to work in GCC 2.8.0 you have to set the
>flag:  -fsjlj-exceptions
Correct.  Robert will probably be releasing a patch to the startup code that
will allow
-fexceptions to work also.  I am probably going to give up on collect2.

>Which I presume uses a different method of exception handling.

Correct also.  Instead of exception tables, where the code goes through a
list of addresses, it uses
setjump/longjump.  SJLJ is more flexible, but it is very slow (it has a big
run time overhead).  Exception
tables has data bloat, but no overhead unless an exception actually occurs.

>What does the flag do and why does it work when the other method of
>exception handling doesn't?
Regular exception handling is expecting the startup code (or Collect2), to
initialize the exception table
before code begins executing.  Currently, thats not happening.

Andy

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