Would there be any difference between both notations when compiling in a .c file or within a .cpp file ?

CodePudding user response：

extern "C" and __declspec(dllimport) are totally orthogonal.

• extern "C" means that C linkage should be used for that symbol. I.e. no C name mangling will be applied. It also limits functions' interfaces to C-compatible things: built-in types, trivial structs, and pointers. Essentially, it tells the compiler and linker that a symbol should be found in the "C way" rather than the "C way". extern "C" is generally used for either calling C functions from C code or creating a C-compatible interface to C code.
• __declspec(dllimport) tells the linker that a symbol will be loaded dynamically at runtime from a DLL.

The two can be combined as well. A function marked extern "C" __declspec(dllimport) will be dynamically linked and use C-style linkage.