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Re: exception handling poll
- To: jfc at mit dot edu (John Carr)
- Subject: Re: exception handling poll
- From: Joe Buck <jbuck at synopsys dot com>
- Date: Fri, 17 Oct 97 10:22:16 PDT
- Cc: rth at cygnus dot com, egcs at cygnus dot com
> 2. Get the overhead for code not using exceptions, but compiled with
> exceptions enabled, under 8% (for "typical" code, whatever that is).
> If that means setjmp exceptions on x86, then we do that.
Um, are you sure? setjmp exceptions put extra code in the text section,
which must be paged in. .eh_frame, on the other hand, is not paged
in normally (or at least, not once it is completely read-only), the
extra space is on disk. Switching to setjmp exceptions means that you
pay more RAM and CPU (since there is overhead even when exceptions are
not thrown). You only save disk space. Is that really a good tradeoff?
> 3. Document and warn that the next egcs release will be binary
> incompatible if exceptions are used.
Well, I think we're going to break compatibility for C++ soon. We
pretty much have to to support namespaces and templated iostreams.
And we'll pretty much want to to get more efficient mangling of
template functions. Just for fun, try looking at the mangled symbols
generated for the methods of map<string,string> .