Stefan Beller <stefanbeller@xxxxxxxxxxxxxx> 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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