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Re: [PATCH][4.3] Deprecate -ftrapv
On Sat, 1 Mar 2008, Richard Guenther wrote:
> I seriously doubt anyone has used it for anything useful since at least
> the advent of tree-ssa. I see we for example warn for -fforce-mem
> in 4.2, but that is a no-op there. Do we have an option to disable
> such warnings? After all it would break -Werror.
-fforce-mem isn't an option affecting the semantics of code the same way
as -ftrapv is, and -ftrapv is more likely to be used manually from time to
time to check for certain types of bugs rather than in makefiles with
-Werror. Telling someone using it manually as a debugging tool that it's
being deprecated seems useful. (NB: we should be clear that it's only the
particular implementation that's proposed for deprecation and removal, and
not the principle of having the -ftrapv feature should someone wish to fix
or reimplement it.)
Bruno Haible used -ftrapv to find bugs in GNU clisp a year ago
<http://gcc.gnu.org/ml/gcc/2007-01/msg00294.html> (that message doesn't
state whether the compiler version was post-tree-ssa). Building without
optimization, as in that case, would I suppose have avoided some of the
-ftrapv bugs.
--
Joseph S. Myers
joseph@codesourcery.com