http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55693
--- Comment #40 from Jack Howarth <howarth at nitro dot med.uc.edu> 2013-01-24
14:54:34 UTC ---
(In reply to comment #39)
My understanding from Nick's comments was that the ld64/dyld behavior is
now as follows. For performance reasons, weak coalescing is only done if the
weak symbols occur in a library (shared or static) and those symbols that are
marked weak in object files are not weak coalesced by dyld. His comments
weren't explicit on that point and I've asked him to confirm that your
work-around of using a static library for the weak symbols isn't exploiting a
'bug' in ld64/dyld that will disappear in a future Xcode release.
I should also note that your patch does produce some regressions on
darwin10 with Xcode 4.2 but this shouldn't shock anyone as we are well aware
that -undefined dynamic_lookup was broken from Xcode 4.2 until it was fixed
again in Xcode 4.4 (radr://10466868). I wouldn't worry about this as...
1) The Xcode 4.x series was never fully supported on darwin10 and only briefly
made available to end-users. Users on darwin10 really need to stick to Xcode
3.2.6 to avoid the -undefined dynamic_lookup bug introduced at Xcode 4.2.
2) Users on darwin11/12 can use any Xcode after 4.4 which are all freely
available from Apple on connect.apple.com.
There is a limit to the number of linker bugs that can be worked around at the
same time in FSF gcc on darwin and I would focus more on those Xcode releases
which provided expected behavior rather than buggy behavior. IMHO, the current
situation is unacceptable for libitm and needs to be fixed since for all modern
(supported) darwin (10/11/12), the stub symbols in crttme.o are overriding
those in libstdc++.
ps On darwin10 with Xcode 4.2, the failures are all of the form...
dyld: Symbol not found: __ZdaPv
Referenced from:
/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin10.8.0/i386/libitm/.libs/libitm.1.dylib
Expected in: flat namespace
in
/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin10.8.0/i386/libitm/.libs/libitm.1.dylib
FAIL: libitm.c/cancel.c execution test
