Define a pre-processor variable for all the files in make

Question

I have a number of .c and .h files with some parts of the code disabled by putting the code block in pre-processor directives e.g.

#ifdef FOOBAR
// some code that can be compiled if needed by defining FOOBAR in pre-processor.
#endif

No I need to define FOOBAR such that its defined for every file that is compiled by gcc using make.

Is there a way to do this with some option to make or Makefile ?

Thanks.

Solution

Add the compiler option -DFOOBAR to the make variable CFLAGS

Comments

[R.. GitHub STOP HELPING ICE]

It should be noted that this is not just a gcc-ism but part of the POSIX standard for C compiler invocation.

[mmtauqir]

Thanks...although I had a few folders each with its own Makefile and I had to add this CFLAGS=... to each one of them, it worked. I wished there was such a thing while calling make. Like e.g. make -flags -DFOOBAR or something similar. But thanks for then answer.

[Jens Gustedt]

@mtahmed, there is. Just put the variable definitions on the command line of make, make CFLAGS='-O3 -march=native -DFOOBAR'

[sherrellbc]

@JensGustedt, Can the variable have a value?

[sherrellbc]

@JensGustedt, Found it (for gcc). -D'macro=definition'. It does not seem to properly work without the outer single quotations. See here.

[x-yuri]

It took me a while to figure out, that I can't just do FOOBAR=1 make.