How to know if a project is C or C++ in Visual Studio?

Question

How does Visual Studio know if a project is C or C++? Is there any configuration or build parameter that indicates this ?

Does VS use C compiler for C, and C++ compiler for C++ ?

Answer 1

Does VS use C compiler for C, and C++ compiler for C++ ?

No

the cl compiler is smart enough to know(based on file extension) if a file is a .cpp or .cc file - which it considers as C++ file. And the cl compiler will consider a .c file as a C program source file, and compile accordingly. Although it does load a separate dll file for compiling C and C++ file. But this is implementation defined.

However, there is a switch to override the behavior of cl based on file extension.

To compile as C++ source file (even with extension of .c), command would be: cl /TP yourfile.c note however, the file should contain valid C++ code.

And to compile as C source file (with extension of .cpp), command would be: cl /TC yourfile.cpp note however, the file should contain valid C code.

Answer 2

Apart from extension, if you go to File Properties->Advanced, there's a Compile As option, which may be used to explicitly treat the code as C code.

It generates /TP for C++ and /TC for C.

As Joachim noted in comments, though, VC++ isn't exactly the most conforming compiler on the planet, so picking "whatever works" might be actually a reasonable option.