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[Bug libc/15756] Check ABI for completeness
- From: "joseph at codesourcery dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Fri, 19 Jul 2013 20:17:35 +0000
- Subject: [Bug libc/15756] Check ABI for completeness
- Auto-submitted: auto-generated
- References: <bug-15756-131 at http dot sourceware dot org/bugzilla/>
http://sourceware.org/bugzilla/show_bug.cgi?id=15756
--- Comment #1 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Such a tools may well be useful to find existing problems and for checking
new architectures (with testing, overlapping tests for similar things can
often be useful), but as I said in
<http://sourceware.org/ml/libc-alpha/2013-07/msg00380.html> I think this
is mainly an API issue not an ABI one.
Taking bug 15666 (alpha __sqrt*_finite) as an example, the real bug isn't
the missing symbols, it's that calling certain functions in code built
with -ffinite-math-only would have resulted in undefined symbols. And
it's not a bug that IA64 doesn't have those symbols, instead having its
own bits/math-finite.h that avoids needing them. Nor is it a bug that
architectures where long double functions are aliases for double functions
don't have *l_finite at all - bits/math-finite.h ensures the right
functions get used in that case. If anything, it's an ABI mistake that
IA64 *does* have the *_finite symbols for Bessel functions (since it gets
those functions from generic libm), even though its bits/math-finite.h
won't use them. (Since those are part of the public ABI now, the only
sensible fix would be to make IA64 bits/math-finite.h use those functions
rather than completely disabling *_finite.)
For all of those architecture variations that aren't bugs, a test that
verifies calling functions with -ffinite-math-only works would work
smoothly in the presence of such variations without needing any special
cases, while detecting the actual bug on alpha before it was fixed, but a
test based on comparing ABI lists would need special cases or manual
architecture maintainer review to determine that the differences are OK.
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