https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62018
Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Target|x86_64-apple-darwin13 |x86_64-apple-darwin1[34]
Last reconfirmed|2014-08-05 00:00:00 |2014-11-9
Component|middle-end |target
Host|x86_64-apple-darwin13 |x86_64-apple-darwin1[34]
Build|x86_64-apple-darwin13 |x86_64-apple-darwin1[34]
--- Comment #9 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
Some more debugging, and finally a victory: I understand what happens. But I
don't know how to fix it.
0. With my testcase from comment #8, compiling with -static-libgcc makes the
executable have the desired behavior (abort), but compiling without it (or with
-shared-libgcc) makes it not abort.
1. Yet forcing to compile with the "shared" object file (_addvsi3_s.o) leads to
correct result (abort). So, it's not a miscomputation.
2. Running the -shared-libgcc executable with DYLD_PRINT_LIBRARIES=y shows that
it's loading the correct libgcc_s:
dyld: loaded: /Users/fx/devel/gcc/irun2/./a.out
dyld: loaded: /usr/lib/libSystem.B.dylib
dyld: loaded: /usr/local/gfortran/lib/libgcc_s.1.dylib
3. But running it with DYLD_PRINT_BINDINGS=y shows that our ___addvsi3 does not
get pulled from libgcc_s.1.dylib, as we'd like, but from the system's
libcompiler_rt.dylib (which has, apparently, a faulty version of this symbol
for backward compatibility reasons):
dyld: lazy bind: a.out:0x10D212010 = libcompiler_rt.dylib:___addvsi3,
*0x10D212010 = 0x7FFF9158BF67
4. And confirmation: forcing it to resolve symbols from libgcc_s.1.dylib, by
saying "DYLD_FORCE_FLAT_NAMESPACE=y
DYLD_INSERT_LIBRARIES=/usr/local/gfortran/lib/libgcc_s.1.dylib", makes the
executable have the expected behavior (aborts).
-----------------------------------
Conclusion: it's really a darwin bug. We need to have symbols taken from our
own libgcc override those from the system's libcompiler_rt (which is itself
pulled from libSystem, if I understand correctly). Any idea how we achieve
that?
