Re: C++ exceptions

On Wed, Jul 04, 2007 at 11:31:30PM +0100, Pedro Alves wrote:
> Kevin O'Connor wrote:
> > I think future versions of gcc wont guarantee function placement
> > relative to top-level asm statements.
> > 
> 
> Ah, you're paying attention. :)  It will certainly fail today if
> we use -ffunction-sections.  If this ever turns into a real problem,
> and we don't have real __try/__except support in the compiler,  we
> can craft an __attribute__((seh ("handler")) into gcc.  I think that
> is much easier.

I get things reordered today when using -O.  Also, I saw on the gcc
website (can't find link now) that they plan on being more aggressive
with this in the future.

> > I'll try to take some of the sample code and integrate it into haret.
> > 
> 
> Great, please do post here your findings.  I'd be curious if you take the
> simplest route of not tweaking the current thread's context and just longjmp
> from the seh handler, and if it brings any real problems (I don't think it's
> safe, but it would be great to be proved wrong).

Attached is what I've done.  Oddly, longjmp directly from the handler
seems to work, but returning via EXCEPTION_CONTINUE_EXECUTION fails.
Not sure what I'm doing wrong.

I use my new handlers with:

    struct eh_data ehd;
    if (start_ehandling(&ehd)) {
        while (wcount--)
            *vaddr++ = value;
        end_ehandling(&ehd);
    } else {
        Output(C_ERROR "EXCEPTION while writing %08x to address %p",
               value, vaddr);
    }

Finally, I call init_ehandling at startup.

-Kevin

exceptions.h
Description: Text document

exceptions.cpp
Description: Text document

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