user/1430: gcc has problems with C++ and exceptions

[Marc Espie <espie@schutzenberger.liafa.jussieu.fr>]

>Number:         1430
>Category:       user
>Synopsis:       gcc has problems with C++ and exceptions
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct  3 08:10:01 MDT 2000
>Last-Modified:
>Originator:     Marc Espie
>Organization:
net
>Release:        
>Environment:
	
	System      : OpenBSD 2.7
	Architecture: OpenBSD.i386
	Machine     : i386
>Description:

As of gcc 2.95.x, g++ has some problems optimizing files that use
exceptions.  This is due to setjump/longjump exceptions creating highly
non-local jumps that tend to force the whole of the file through
optimization 

>How-To-Repeat:

Compile kde-1.94. Observe g++ memory usage going thru the rooftop and
beyond on a few files (stopped it at 300M).
Observed on a 386, likely to occur elsewhere.

>Fix:

Add primitives needed to support dwarf2 exceptions (known) and activate
exceptions through dwarf2 unwinds. As long as C++ shared libraries are 
linked with gcc -shared, collect2 will add the required 
register_frame_info/deregister_frame_info.

The intermediate code produced has much better locality, and doesn't bug
g++ as much.

make sure the code works correctly (currently, kde2 with dwarf2 unwinds
hangs in exit()), test release, activate.

Alternately, switch to elf, and native dwarf2 unwinds should come
naturally.

>Audit-Trail:
>Unformatted: