Re: [PATCH 8/8] hook-list.h: add a generated list of hooks, like config-list.h

On Tue, Nov 16 2021, Mike Hommey wrote:

On Mon, Nov 15, 2021 at 11:49:31PM +0100, Ævar Arnfjörð Bjarmason wrote:

quoted

On Tue, Nov 16 2021, Mike Hommey wrote:

quoted

On Mon, Nov 15, 2021 at 11:26:36PM +0100, Ævar Arnfjörð Bjarmason wrote:

quoted

On Tue, Nov 16 2021, Mike Hommey wrote:

quoted

On Thu, Sep 23, 2021 at 12:30:03PM +0200, Ævar Arnfjörð Bjarmason wrote:

quoted

-builtin/help.sp builtin/help.s builtin/help.o: config-list.h GIT-PREFIX
+hook.sp hook.s hook.o: hook-list.h
+
+builtin/help.sp builtin/help.s builtin/help.o: config-list.h hook-list.h GIT-PREFIX

hook-list.h is only included from buitin/bugreport.c, so
builtin/bugreport.o should be the one with the hook-list.h dependency,
shouldn't it?

Well spotted, yes. This is a mistake. I think from some earlier WIP
version of the series.

In practice we don't really miss dependencies due to these sorts of
mistakes since we use the .depends files, i.e. GCC & Clang figure this
out for us:

    $ grep hook-list .depend/* */.depend/*
    builtin/.depend/bugreport.o.d: compat/compiler.h git-compat-util.h hook.h hook-list.h
    builtin/.depend/bugreport.o.d:hook-list.h:

But aren't those .depends files are only created when compiling object
files, such that builtin/.depend/bugreport.o.d wouldn't exist until
bugreport.c is compiled, which would fail if hook-list.h wasn't created
before that?

Fail how?

I don't think it could fail, because the purpose of these dependency
relationships is to avoid needless *re*builds. So if you're building for
the first time it doesn't matter, your compiler will find the relevant
things to include for you. It doesn't need what's in the Makefile to do
that.

See [1], what I said about LIB_H there applies more generally for the
.depends files.

It will only fail in the sense that it over-depends, i.e. if you do:

    git clean -dxf; make builtin/help.o

Try

    git clean -dxf; make builtin/bugreport.o

It fails with:

      CC builtin/bugreport.o
  builtin/bugreport.c:7:10: fatal error: hook-list.h: そのようなファイルやディレクトリはありません
      7 | #include "hook-list.h"
        |          ^~~~~~~~~~~~~
  compilation terminated.
  make: *** [Makefile:2500: builtin/bugreport.o] エラー 1

The only reason I can see why it builds at all normally is that hook.o
is built soon enough that by the time builtin/bugreport.o is built
hook-list.h has already been generated.

Ah, you're obviously right. I don't know what I was thinking yesterday.

I submitted a re-roll of the greater dependency fix-up & optimization
series I've got kicking around, which includes a fix for this
issue. Thank you for the report:
https://lore.kernel.org/git/cover-v3-00.23-00000000000-20211116T114334Z-avarab@gmail.com (local)