[Bug fortran/55891] Problem with shared library and EQUIVALENCE on darwin 11.4.2 x86_64

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55891

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-01-22 11:52:27 UTC ---
Form
https://groups.google.com/forum/?fromgroups=#!topic/comp.lang.fortran/E_ll5RFNL14
FX said:

Compiling shared libraries on Darwin is a bit more tricky than on your 
typical Linux system. 

In your case, you're missing -flat_namespace: 

   Two-level namespace 
     By default all references resolved to a dynamic library record the 
     library to which they were resolved. At runtime, dyld uses that informa- 
     tion to directly resolve symbols.  The alternative is to use the 
     -flat_namespace option.  With flat namespace, the library is not 
     recorded.  At runtime, dyld will search each dynamic library in load 
     order when resolving symbols. This is slower, but more like how other 
     operating systems resolve symbols. 

(from Mac OS ld man page). Typical use case for creating a Darwin shared 
library is: 

$ gfortran -dynamiclib -undefined suppress -flat_namespace -fPIC  mod.f90 -o
libfoo.dylib 
$ gfortran main.f90 -lfoo -L. && ./a.out 
          40          40 

This PR should probably be closed as INVALID.