Wednesday, May 19, 2010

extern "C" - demystified

This post is about extern "C", See other posts (in the pearl blog) on other uses of extern.

extern "C" is the only form in the standard. It is designed to help linking with Fortran, C or even other c++ modules. See the chapter in [[moreEffC++]]

Basic purpose on functions? suppress name mangling.

Why mangling? See moreEffC++.

extern-c wraps func prototypes. You can make extern-c wrap func implementations, but not common.

linker -- extern is a linkage feature.

Interaction with #include? See c++Primer

-- Repeated declarations ?
Forget about extern-c first. Given any given function prototype, it can appear multiple times even in "rapid fire", like void a(); void a(); void a(). Compiler just ignores them. Extern-c doesn't change the rule. See p366 c++Primer.

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