shared libraries symbols visibility

[David Froger]

Hi list,

Python documentation on Extending Python with C or C++ says [1]:
    When modules are used as shared libraries, however, the symbols defined
    in one module may not be visible to another module.

Suppose I have an extension module that call functions provided by a shared
library, for example blas. Do I meet the same portability issue? If not, Why?

Thanks for your replies.
David

[1] http://docs.python.org/2/extending/extending.html#providing-a-c-api-for-an-extension-module