GCC Merge two differents object files to one object file

Question

 // f.for is a Fortran source file
 // c.c is a C source file   
 # gfortran -c f.for            // produce f.o
 # gcc -c c.c                   // produce c.o

since f.for calls some functions from c.c. How can I produce a third object file fc.o which will be used later to generate an executable with another C source code. explain:

 # gcc/gfortran? (or other) -?? f.o c.o -o fc.o
 # gcc -o executable source.c fc.o

thank you

What I have done but not work:

  # ar rvs fc.a f.o c.o  
  # gcc -o executable source.c fc.a

But it shows me error like : undefined reference to 'function_name_X'. function_name_X is in f.for

`ar rvs fc.a f.o c.o` will get you a static library (`fc.a`), which you can use as if it were an object file made by merging `f.o` and `c.o`. — Petr Skocik, Oct 22 '15 at 21:03
PSkocik: Yes, I'll try again this solution, perhaps it is the unique solution — Phiber, Oct 22 '15 at 21:08
Have you tried `ld -r f.o c.o -o fc.o`, then? (Dark Falcon's link) — Petr Skocik, Oct 22 '15 at 21:08
You may be asking the wrong question. If you're producing all these object files in the same build process, then you don't need to make a combined object file. You can just link all the needed object files together to produce the final executable. — John Bollinger, Oct 22 '15 at 21:10
John Bollinger -> I have this this idea in my mind: if a.o depends on b.o, c.c depends on a.o , so # gcc -o exe c.c a.o b.o will work? — Phiber, Oct 22 '15 at 21:13

score 1 · Answer 1 · edited May 23 '17 at 12:01

Credit: PSkocik, John Bollinger
My comment :

I have this this idea in my mind: if a.o depends on b.o, c.c depends on a.o , so # gcc -o exe c.c a.o b.o will work?

should works. In fact, I listed all functions in f.o :

 # nm f.o

I find that Fortran add underscore '_' at the end of every function name, since I'm calling these functions from C without adding underscore at end, this error happened. According to this question: I added -fno-underscoring to gfortran compiler when generating f.o

# gfortran -c f.for -fno-underscoring
# nm f.o

at this time, there is no underscore at the end.
Response to the question:

# gcc -o executable source.c f.o c.o  // not need fc.o

GCC Merge two differents object files to one object file

1 Answers1