Preprocessing in two or more C sources

[Claudio Bley]

>>>>> "Radu" == Radu ION <radu@racai.ro> writes:

    Radu> Hello Problem : there are given 3 files : header.h,
    Radu> source1.c, source2.c. The header is included in both
    Radu> source1.c and source2.c and contains some global definitions
    Radu> of variabiles. After compilation, the linker complained that
    Radu> he saw redefinitions.  So, the whole header.h is now
    Radu> enclosed by : #ifndef NAME #define NAME (on separate lines)
    Radu> and #endif The problem is still there. I can workaround
    Radu> this, but I don't understand.  My compile command was : gcc
    Radu> -Wall -ggdb source1.c source2.c -o runme My logical
    Radu> assumption was that gcc should remember all the #define NAME
    Radu> directives and behave accordingly on subsequent
    Radu> preprocessing on sources. It appears that every source is
    Radu> preprocessed independently and so, the preprocessing is done
    Radu> once per source file without state information being
    Radu> exchanged (i.e. in source2.c NAME, should have already been
    Radu> defined) Is that true ?

Yes, it is true that the files are processed independently of each
other. You shouldn't define instances of (global) variables in any
header file. You need to declare them 'extern' (forward declaration)
and define them only at one location.

    Radu> Does GNU Make know about this sort of problems ? 

I guess no, it's a programming problem.

    Radu> I wonder if I can use make to set up some 'project'
    Radu> enviroment like in MSVC++ for instance.

I never used MSVC++, I don't know.

Claudio