"Richard Guenther" <[EMAIL PROTECTED]> writes: > Authors of the affected programs should adjust their makefiles
That is what the proposed patch is for. It gives a way for developers to adjust their makefiles. A developer of portable software cannot simply put something like this into a makefile: CFLAGS = -g -O2 -fwrapv as -fwrapv won't work with most other compilers. So the developer needs some Autoconfish help anyway, to address the problem. The proposed help is only rudimentary, but it does adjust makefiles to address the issue, and it's better than nothing. Further improvements would of course be welcome. > the much more often reported problems are with > -fstrict-aliasing, and this one also doesn't get any > special treatment by autoconf. That's a good point, and it somewhat counterbalances the opposing point that -O2 does not currently imply '-ffast-math'ish optimizations even though the C standard would allow it to. I don't feel a strong need for 'configure' to default to -fstrict-aliasing with GCC. Application code that violates strict aliasing assumptions is often unportable in practice for other reasons, and needs to be rewritten anyway, even if optimization is disabled. So -fstrict-aliasing wouldn't help that much. In contrast, the wrapv assumption is relatively safe and does not need to be rewritten to be widely portable in practice, under the assumptions documented in the proposed patch. Also, my admittedly anecdotal impression is that the wrapv assumption is more pervasive. I don't know of any strict aliasing assumptions in coreutils, for example, but I know of several wrapv assumptions. I suspect the same thing is true for many other GNU applications. All that being said, I have no real objection to having Autoconf default to -fstrict-aliasing too. However, I'd rather not propose that change right now; one battle at a time. > -O2 is what gets the most testing, Another good point, but if this change goes through Autoconf -O2 -fwrapv will get a lot of testing in real-world C applications, and that will help mitigate any problems in this area.
