CODEWITHSUNDEEP
c++gcc
manatttta
manatttta

Reputation: 3130

GCC: check if compiling as library or executable

I have some class implementation that is going to function as a Lib. However, I want to include a main function in that library with a simple driver testing my class. The function main can therefore be only compiled if I define my compilation target as an executable.

Can this be done via some macro or similar?

I would not like to create a new project nor Makefile, just a simple #ifdef wrapping the main function would be perfect for this job.

Upvotes: 0

Views: 1278

Answers (2)

Aracthor
Aracthor

Reputation: 5917

You can define a macro with the -D option of GCC. For instance, you can define a macro _RELEASE with option -D_RELEASE and wraps as the following:

#ifdef _RELEASE
// Release main
int main()
{
    // ...
}

#else
// Another main
int main()
{
    // ...
}

#endif

You can compile a main or another by adding -D_RELEASE to your compilation line:

gcc main.c -D_RELEASE [other flags] # compile with release main
gcc main.c [other flags] # compile with other main

NOTE

This is an example for a main function, but of course it can be implemented for any function in a library.

Upvotes: 2

MSalters
MSalters

Reputation: 180205

No, this can't be done by a macro. Wrong phase of compilation. Both C and C++ have 3 relevant steps: Per Translation Unit, the preprocessor and the compiler itself are run. Finally, the TU's are linked together by the linker.

While preprocessing or compiling an individual TU, you can't know what other TU's might contain, or what you will be linked into. In fact, it's quite possible that the makefile defines rules either way. E.g. file1.obj might go both into A.LIB and A.EXE.

Upvotes: 0

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