Re: Use of -fno-exceptions

[Jeff Sturm <jsturm at one-point dot com>]

On Mon, 19 Nov 2001, Joe Buck wrote:
> > > The exceptions support is needed to do a cleanup.  When an exception
> > > is thrown, the stack gets popped one frame at a time and destructors
> > > are called, up to the point where the exception is caught.  For this
> > > to work properly, every possible call site that could be involved
> > > would need to be compiled with exceptions enabled.  You may be able
> > > to make a mixed environment work, but it will be tricky and perhaps
> > > unstable.
> > 
> > Is that strictly true?  My understanding is that one could use
> > sjlj-exceptions and throw over any call frame, compiled with -fexceptions
> > or not, because setjmp/longjmp processing doesn't require explicit unwind
> > info.
> 
> For a call frame where a destructor must be called, even with sjlj you
> need -fexceptions to get that destructor called.  Otherwise there will
> be a memory leak and possibly some resource that should be freed won't
> be (like a lock for a critical region, if managed with a constructor/
> destructor pair).

You're right.  I was thinking about the common case in which I have a C
library compiled without -fexceptions.  Since C doesn't have destructors,
I can get by with sjlj-exceptions.

Jeff