Re: [PATCH resend] Makefile: Use computed header dependencies if the compiler supports it

Hi,

Fredrik Kuivinen wrote:

Previously you had to manually define COMPUTE_HEADER_DEPENDENCIES to
enable this feature. It seemed a bit sad that such a useful feature
had to be enabled manually.

Yes!  Thanks for this.

I have a few thoughts about the implementation:

[...]

This causes "make foo" to run gcc and create a temporary file
unconditionally, regardless of what foo is.  In an ideal world:

 - the autodetection would only happen when building targets that
   care about it

 - the detection would happen once (creating some file to store the
   result) and not be repeated with each invocation of "make"

 - (maybe) there would be a way to override the detection with
   either a "yes" or "no" result, for those who really care to
   save a little time.

I was about to say that the GIT_VERSION variable has some of these
properties, but now that I check, from the point of view of the
Makefile it doesn't.  ./GIT-VERSION-GEN is just very fast. :)

I wonder if we can make do with a faster check, like

	$(CC) -c -MF /dev/null -MMD -MP git.c --help >/dev/null 2>&1

What do you think?