------- Comment #9 from dave at hiauly1 dot hia dot nrc dot ca 2009-04-21
17:28 -------
Subject: Re: [4.4/4.5 regression] symbol __signb...@glibcxx_3.4 in libstdc++
not exported anymore
> > I believe the problem is the symbol was exported when it shouldn't have
> > been.
>
> How?
This is probably because __signbitl is not present in libc and libm.
hppa-linux doesn't need __signbitl because sizeof(long double)==sizeof(double).
"l" library functions just call __signbit. Thus, I believe that the lack
of __signbitl in glibc caused this preoblem.
__signbitl doesn't seem to be required by POSIX. However, LSB 2.1
specifies it. If __signbitl should be provided by glibc, then this
is a glibc bug.
The signbit macro is as follows:
/* Return nonzero value if sign of X is negative. */
# ifdef __NO_LONG_DOUBLE_MATH
# define signbit(x) \
(sizeof (x) == sizeof (float) ? __signbitf (x) : __signbit (x))
# else
# define signbit(x) \
(sizeof (x) == sizeof (float) \
? __signbitf (x) \
: sizeof (x) == sizeof (double) \
? __signbit (x) : __signbitl (x))
# endif
This will fail if the call to __signbitl isn't optimized away. So, either
the macro needs to be fixed, or __signbitl needs to be provided by glibc.
The isfinite macro would have the same problem, but in that case
glibc provides __finitel.
> > The signbit macro is provided by math.h.
>
> But it's not in the baseline files showing that it is exported. This question
> was originally asked here:
>
> http://gcc.gnu.org/ml/gcc-patches/2008-03/msg00197.html
Why should a macro be exported?
Dave
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39491
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