Stefan Beller <stefanbel...@googlemail.com> writes: > From my understanding there is no > difference for functions declarations being set to extern or not, > because extern is the default on functions.
There is a difference for shared libraries if you would like to control which symbols are exported. With gcc, for example, you might compile using -fvisibility=hidden. Any functions explicitly declared with extern, bearing __attribute__((visibility("default")), or using visibility pragmas will be exported (similar to __declspec(dllexport) on Windows). Other functions will be internal to the shared library so you don't have to worry about callers depending on those symbols and performance can be a bit better by skipping the PLT and avoiding symbol relocations at load time. See Drepper's guide for more. http://www.akkadia.org/drepper/dsohowto.pdf
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