On Thu, Feb 23, 2023 at 11:35 AM Junio C Hamano <gitster@xxxxxxxxx> wrote: > > "Elijah Newren via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes: > > > From: Elijah Newren <newren@xxxxxxxxx> > > > > Since git-compat-util.h needs to be included first in C files, having it > > appear in header files is unnecessary. More importantly, having it > > included in header files seems to lead to folks leaving it out of C > > files, which makes it harder to verify that the rule is being followed. > > Remove it from header files, other than the ones that have been approved > > as alternate first includes. > > Hmph, doesn't this cut both ways? > > I like the idea that the removal of compat-util from other > header files may increase the likelihood that a C file that includes > such header files without including compat-util fail to compile, > because it would fail to find what is defined or declared in > compat-util. > > But from "include what you use" point of view, shouldn't a header > that defines or declares its own stuff using what is defined or > declared in compat-util be including compat-util itself? > > Or do I misunderstand what "make hdr-check" is trying to achieve? > > Granted that the check does not fail with this patch in place, but I > suspect that it is by accident (i.e. there happens to be nobody who > depends on what is defined/declared in compat-util for their own > definition or declaration). Also I am not sure how to interpret > the fact that "make hdr-check" succeeds with this patch. Does it > mean C files that include these header files while forgetting to > include compat-util may not be caught by the compiler after all? > > So, I dunno. I did something like that before, and Peff objected; see https://lore.kernel.org/git/20180811173406.GA9119@xxxxxxxxxxxxxxxxxxxxx/ and https://lore.kernel.org/git/20180811174301.GA9287@xxxxxxxxxxxxxxxxxxxxx/. I think for sanity we should do one of the following: (a) make C and header files both depend upon everything they need (b) consistently exclude git-compat-util.h from headers and require it be the first include in C files I think things get really messy if we let half the headers follow (a) and the other half are forced to do (b). I was pushed towards (b) before, but now that I've worked on this series, I think there is even more reason to go this direction: this work I did during this series shows that if we allow a mixture of (a) and (b), then empirically we end up with C files that don't include git-compat-util.h directly, and those same C files likely include some headers that don't include git-compat-util.h at all, and if the other headers are included before the indirect inclusion of git-compat-util.h then there are risks that things will break in very subtle ways (as pointed out by Peff in the above-linked emails). So, I'm inclined to go towards (b).
