In C how do I compile and then create an executable file with a header and two c files?

Question

I have three C files in total. One is a header [.h] file, two are source [.c] files.

The .h file is called encryption.h and the corresponding source file is encryption.c. The encryption.c has logic, but no main() function. My second c file is called main.c. There I have the main() function that calls methods from encryption.c.

I am compiling these files within terminal on Mac OSx. I am confused on how to compile this, I have tried the following:

gcc -c main.c gcc -c encryption.c gcc -c encryption.h gcc main.o encryption.o encryption.g.gch -o encrypt

This doesn't seem to work though, it says I have a precompiled-header already. I tried finding the answer online, I know it has to be simple, but I haven't had much luck. What is the issue here?

Thank you @SouravGhosh. What would be the appropriate way of going about this? — Miguel J.
– Miguel J., Commented Apr 15, 2015 at 12:18
Just don't compile the header file, and don't link with the precompiled header file, only the object files generated from the source files. — Some programmer dude
– Some programmer dude, Commented Apr 15, 2015 at 12:19
I don't know, evidently whatever happens to a compiled .h file with gcc.... — Miguel J.
– Miguel J., Commented Apr 15, 2015 at 12:51
From what I looked up online they're precompiled header files used to optimize performance in some aspect. @JoachimPileborg — Miguel J.
– Miguel J., Commented Apr 15, 2015 at 12:53

Sourav Ghosh · Accepted Answer · 2015-04-15 12:25:26Z

5

Don't compile the header file. Header files are meant to be included to the source files (using #include directive, in c). Just compile the source files and link them together. Something like

gcc -c main.c gcc -c encryption.c gcc main.o encryption.o -o encrypt

or, for shorthand,

gcc main.c encryption.c -o encrypt

^{Note: If you're bothered about the presence (or absence) of header files while compilation, check the pre-processed output of each source files using gcc -E option.}

edited Apr 15, 2015 at 12:25

answered Apr 15, 2015 at 12:19

Sourav Ghosh

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3 Comments

Miguel J. Over a year ago

What's the point of the header file then? I am really familiar with Java, and I see the header file like an interface. Is there no point in having it if it's not going to be used then? I mean unless there are constants in the header file, then that's a different story, but my professor wants the skeleton code for my functions in that file. . .

Sourav Ghosh Over a year ago

@MiguelJ. Updated the answer. Hope that helps. :-)

pmg Over a year ago

The point of header files is, basically, so that every code file which #includes it knows how the functions declared there work. Also knows about #defines and types ...

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