[Bug lto/49992] lto-bootstrap reveals duplicate symbols on x86_64-apple-darwin11

["howarth at nitro dot med.uc.edu" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49992

--- Comment #10 from Jack Howarth <howarth at nitro dot med.uc.edu> 2011-08-08 19:27:58 UTC ---
This is radar://6320843 "duplicate symbols from static libraries not properly
ignored" revisiting us...

26-Oct-2008 10:43 AM Jack Howarth:
Xcode 3.2 fails to link cc1plus-dummy from gcc 4.3.2 due to a reappearance of
radar 5808800//5779681 which was appeared and was fixed during the Xcode 3.1
development cycle. The bug causes the following link failure while building FSF
gcc 4.3.2...

etc.

Their response was...

06-Nov-2008 03:04 PM KIT CHEUNG :
Engineering has requested the following information in order to further
investigate this issue:

How was libbackend.a created?  Its table of contents is wrong because it
contains entries for tentative definitions.  

We ran ranlib on libbackend.a then bad_link_command succeeded.  

If you run:
   ranlib -c libbackend.a
then bad_link_command fails again.   

So my guess is that the build used the -c option when creating libbackend.a. 
Is there a reason for this? 

Darwin static archives traditionally do not have common symbols in there table
of contents.  The -c option forces common symbols into the table of contents
and causes this problem.