C++ can use c functions by extern "C",
can c use c++ functions somehow?
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4 Answers
Not really. You can write a "C-compatible" function in C++, that is to say outside of any class or namespace and whose prototype does not use classes or references. If declared extern "C" then you could call such a function from C. The function could then go on to make use of whatever C++ features were useful for it.
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compile-fan
can the c++ function declared extern "C" use any other classes in its function body?
Just the same way, if you declare a C++ function as extern "C", C will be able to link with it.
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When it comes to functions in c++, there are two types that come to mind: plain-old stand alone functions and member functions that're part of a class. There is no way to use the second type directly in C since it has no notion of an 'object'. Remember member functions have an implicit 'this' as a hidden first parameter.
You can, however, use the first type of function in C if you decorate it with the extern "C" declaration as part of the function prototype. This is needed to tell the C++ compiler to not 'mangle' the function name when you compile your source.
3 Comments
compile-fan
what if the plain-old stand alone functions uses other classes in its function body,can it still be used directly in c?
greatwolf
@compile-fan that is possible but only if you compiled that function in C++ mode and then link into your C code afterwards as a library or object file. The key observation here is you have to keep C++ specific code isolated behind that boundary.
mmmmmm
@compile-fan - the C++ code can be called from C but the function is in C++
C can use C++ functions only as functions from an external library.
Better way is to compile your C code with help of C++ compiler. Look here, please: http://www.velocityreviews.com/forums/t288284-calling-c-from-c.html
