On UNIX System V descendent systems, during program runtime the dynamic linker resolves weak symbols definitions like strong ones. For example, a binary is dynamically linked against libraries libfoo.so and libbar.so. libfoo defines symbol codice_9 and declares it as weak. libbar also defines codice_9 and declares it as strong. Depending on the library ordering on the link command line (i.e. codice_11) the dynamic linker uses the weak f from libfoo.so although a strong version is available at runtime. The GNU codice_12 provides the environment variable codice_13 to provide weak semantics for the dynamic linker.