[Bug libstdc++/39491] [4.4/4.5 regression] symbol __signbitl@GLIBCXX_3.4 in libstdc++ not exported anymore

["bkoz at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #23 from bkoz at gcc dot gnu dot org  2009-04-23 17:16 -------

So:

* Original submitter is incorrect, there has never been a
__signbitl@GLIBCXX_3.4 symbol, and there should not be one now?

Right. This should have manifested as an abi-check FAIL starting in gcc-4.2, as
a new symbol was added with the original version label. So gcc-4.2/4.3 had a
regression from gcc-4.1 that gcc-4.4 fixed.

That regression is
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32666

>From that first log:
http://gcc.gnu.org/bugzilla/attachment.cgi?id=13863&action=view

You see:
65
__signbitl
version status: incompatible
GLIBCXX_3.4
type: function
status: added


>From this I conclude that the libstdc++ abi checking was working, but ignored
for 4.2 and the 4.3 release on this platform. That's ok, everybody was busy and
there were some issues, but for 4.4 we are back on it.

Of course, on the meta level, libstdc++ doing this math library hacking is just
wrong and prone to failure: we want the C99 math library assumed and underneath
us in either gcc support libs or at the libc level. That's why gcc-4.4/trunk
tries to flee from this area after attempting to burn the remains of libmath.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39491