On Mon, Sep 10, 2012 at 04:38:58PM +0200, Joachim Schmitz wrote:
> >More importantly, though, is it actually portable? I thought it was
> >added in C99, and we try to stick to C89 to support older compilers
> >and systems. My copy of C99 is vague (it says only that the "bool"
> >macro was added via stdbool.h in C99, but nothing about the "true"
> >and "false" macros), and I don't have a copy of C89 handy. Wikipedia
> >does claim the header wasn't standardized at all until C99:
> >
> > https://en.wikipedia.org/wiki/C_standard_library
>
> Indeed stdbool is not part of C89, but inline isn't either and used
> extensively in git (could possible be defined away),
You can define INLINE in the Makefile to disable it (or set it to
something more appropriate for your system).
> as are non-const array intializers, e.g.:
>
> const char *args[] = { editor, path, NULL };
> ^
> ".../git/editor.c", line 39: error(122): expression must have a
> constant value
>
> So git source is not plain C89 code (anymore?)
I remember we excised a whole bunch of non-constant initializers at some
point because somebody's compiler was complaining. But I suppose this
one has slipped back in, because non-constant initializers are so damn
useful. And nobody has complained, which I imagine means nobody has
bothered building lately on those older systems that complained.
My "we stick to C89" is a little bit of a lie. We do not care about
specific standards. We do care about running everywhere on reasonable
systems. So something that is C99 might be OK if realistically everybody
has it. And something that is POSIX is not automatically OK if there are
many real-world systems that do not have it.
Since there is no written standard, there tends to be an organic ebb and
flow in which features we use. Somebody will use a feature that is not
portable because it's useful to them, and then somebody whose system
will no longer build git will complain, and then we'll fix it and move
on. As reviewers, we try to anticipate those breakages and stop them
early (especially if they are ones we have seen before and know are a
problem), but we do not always get it right. And sometimes it is even
time to revisit old decisions (the line you mentioned is 2 years old,
and nobody has complained; maybe all of the old systems have become
obsolete, and we no longer need to care about constant initializers).
Getting back to the patch at hand, it may be that stdbool is practically
available everywhere. Or that we could trivially emulate it by defining
a "true" macro in this case. But it is also important to consider
whether that complexity is worth it. This would be the first and only
spot in git to use "true". Why bother?
-Peff
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