-fexceptions? -fasync-unwind-tables?

[Gregory M. Turner]

OK, as you may have guessed, I'm still driving myself insane trying to fix 
__try and friends.  I have some other less promising ideas on the backburner; 
this one seemed to have sufficient potential that I thought I would ask the 
group to let me know what they think.

In short: gcc accepts the above options.  The first, is considered to be a C++ 
compatibility mode in C.  That is to say, it provides the right glue such 
that exceptions can unwind through calls to C libraries.  If /any/ library in 
the call-chain leaves this option out, I'm afraid it breaks down.

The second, -fasync-unwind-tables, provides "dwarf2 unwind tables".  I've 
looked through the dwarf2 spec and some other sources, but I have yet to find 
solid documentation for this... perhaps it's a "use the source, Luke" 
situation.  But this second option promises "instruction-granularity" unwind 
tables of some kind.  IOW, presumably, this would be enough to implement 
__try and friends without looking beyond the stack pointer.

As for the idea of stealing the return pointer on the stack.  I like it even 
less now.  It appears that signal handlers are allowed to clobber the stack 
above the SP on some architectures, which means we're pretty much up a creek.
There still might be some ultra-clever work-around involving copying the 
current stack frame, but I think we would at least have to create our own 
trampolines in asm, which, I fear, might break in subsequent gcc releases...

So... anybody know where these options are actually documented?  I mean, I see 
the blurb in the info pages, which is enticing, but surely there is some API 
or datastructure to look at somewhere....

-- 
"Security is mostly superstition. It does not exist in nature,
nor do the children of men as a whole experience it. Avoiding
danger is no safer in the long run than outright exposure. Life is
either a daring adventure, or nothing. To keep our faces toward
change and behave like free spirits in the presence of fate is
strength undefeatable." --Helen Keller

gmt