CODEWITHSUNDEEP
c++makefile
Drew
Drew

Reputation: 1261

g++ makefile, multiple cpp's each with there own main()

I have several .cpp files that each are compiled separately into their own executables, I also want to use the functions in each of them with .h in a main executable. How do I go about doing this?

makefile

all: A B C
  g++ -o main.exe -std=c++11 A.cpp B.cpp C.cpp

A: A.cpp
  g++ -o A.exe -std=c++11 A.cpp


B: B.cpp
  g++ -o B.exe -std=c++11 B.cpp


C: C.cpp
  g++ -o C.exe -std=c++11 C.cpp

Upvotes: 0

Views: 128

Answers (2)

rodrigo
rodrigo

Reputation: 98516

A C program cannot have two functions with the same name, main is not special in that.

My advice is to separate the main functions to their own CPP files and leave only the utility reusable functions in the common files:

all: A B C
  g++ -o main.exe -std=c++11 all_main.cpp A.cpp B.cpp C.cpp

A: A.cpp
  g++ -o A.exe -std=c++11 A_main.cpp A.cpp


B: B.cpp
  g++ -o B.exe -std=c++11 B_main.cpp B.cpp


C: C.cpp
  g++ -o C.exe -std=c++11 C_main.cpp C.cpp

An alternative would be to use conditional compilation to skip the undesired main definitions. But that would be quite messy.

Something like:

A.cpp

void funA()
{ /*...*/ }

#ifdef A_EXE
int main()
{
}
#endif

And then in the makefile:

A: A.cpp
  g++ -o A.exe -std=c++11 -DA_EXE A.cpp

This use of conditional compilation trick, although a bit hacky and not very extensible, is used some times to provide a small test case or sample program within the code of a library.

Upvotes: 2

user3159253
user3159253

Reputation: 17455

Well, if main() in each of A.cpp, B.cpp, C.cpp is absolutely necessary, then you can put it under #ifdef:

#ifdef STANDALONE_APP
int main(....) { ... }
#endif

and then pass -DSTANDALONE_APP for each of A, B, C...

Or maybe better use the advice of @rodrigo.

Upvotes: 1

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