[Scons-users] -BSymbolic when linking shared libraries

[Hartmut.Brandt at dlr.de]

Hi,

I figured out a nasty problem with building shared libraries: when building the library with cmake, everything is fine, when building it with scons the test programs fail in strange manners. After digging around, I found out that scons uses the -Wl,-Bsymbolic unconditionally  on posix platforms when linking shared libraries when cmake does not.

After digging around in the internet I think, that this is wrong. The very nice paper on shared objects and libraries by Ulrich Drepper (http://www.akkadia.org/drepper/dsohowto.pdf) says: "The advice here is to never use DF_SYMBOLIC. It does not improve the code, forces all symbols to be treated the same, and can cause problems in symbol lookup. It is mentioned here only for completeness and as a warning.". Intel warns in https://software.intel.com/en-us/articles/performance-tools-for-software-developers-bsymbolic-can-cause-dangerous-side-effects: "So as soon as you turn on -Bsymbolic for C++ or Fortran you might expect trouble."

In fact, it breaks static class member variables in shared libraries in rather subtle ways. Unfortunately it is hard coded in Tool/__init__.py (VersionedSharedLibrary()) so that it is not so easy to switch off.

Can we remove this flag or at least make it configurable in some way?

harti