Feature request: Warning when .c file gets #include'd

["Jiří Wolker" <woljiri@gmail.com>]

Hi,

I've met a guy that is learning C and got stuck when the linker produced
a screenful of messages about that he did something define multiple
times. The cause of the problem was trivial:

    He did ``#include "something.c"'' in his code.

In the past, I also did this thing multiple times and I would appreciate
a warning produced by the gcc when compiling C/C++ file that includes a
file ending in .c, .cx, .cpp or .cxx.

What do you think about that?

I would prefer to make this enabled when -Wextra is used.

Based on my past experience with using .c files in the include
directive, I can think of these problems.

  - Sometimes, I want to include a file that is definitely not a header,
    but also it is not a stand-alone source file. I personally prefer
    using .inc suffix, but some people possibly terminate the file names
    with .c suffix like a source file.

    Example:  list of enum fields included from a separate file that was
              generated by a script

  - In some projects, someone can deliberately want to include another
    source file. For example, this can happen when doing unit tests and
    you do not want to specify the source file name on the command line.

If you accept that, I can try to implement that. (That would be my first
contribution to this project and I do not know gcc codebase, but it
looks like a relatively simple change.) Do you think that it would need
a copyright assignment?

Thanks,
Jiří