Subject: Re: [PATCH] run-command.c: fix missing include under `NO_PTHREADS`

From: Taylor Blau <[email-masked]>
Date: Tue, 16 May 2023 17:33:43 -0400

On Tue, May 16, 2023 at 12:12:02PM -0700, Junio C Hamano wrote:
> Taylor Blau <[email-masked]> writes:
>
> > When building git with `NO_PTHREADS=YesPlease`, we fail to build
> > run-command.o since we don't have a definition for ALLOC_GROW:
> >
> >     $ make NO_PTHREADS=1 DEVELOPER=1 run-command.o
> >     GIT_VERSION = 2.41.0.rc0.1.g787eb3beae.dirty
> >         CC run-command.o
> >     run-command.c: In function ‘git_atexit’:
> >     run-command.c:1103:9: error: implicit declaration of function ‘ALLOC_GROW’ [-Werror=implicit-function-declaration]
> >      1103 |         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
> >           |         ^~~~~~~~~~
> >     cc1: all warnings being treated as errors
> >     make: *** [Makefile:2715: run-command.o] Error 1
>
> I am OK to give a reproduction recipe, i.e. the "$ make" command
> line, to make it easy for people, who cannot remember how to define
> make variables from the command line, to try out themselves, but I
> hate the "build transcript" in the log message, when a few lines of
> prose suffices.

Much appreciated. Here's a version with your changes include that is
suitable for queueing:

--- 8< ---

Subject: [PATCH] run-command.c: fix missing include under `NO_PTHREADS`

Git 2.41-rc0 fails to compile run-command.c with `NO_PTHREADS` defined,
i.e.

  $ make NO_PTHREADS=1 run-command.o

as `ALLOC_GROW()` macro is used in the `atexit()` emulation but the
macro definition is not available.

This bisects to 36bf195890 (alloc.h: move ALLOC_GROW() functions from
cache.h, 2023-02-24), which replaced includes of <cache.h> with
<alloc.h>, which is the new home of `ALLOC_GROW()` (and
`ALLOC_GROW_BY()`).

We can see that run-command.c is the only one that try to use these
macros without including <alloc.h>.

  $ git grep -l -e '[^_]ALLOC_GROW(' -e 'ALLOC_GROW_BY(' \*.c | sort >/tmp/1
  $ git grep -l 'alloc\.h' \*.c | sort >/tmp/2
  $ comm -23 /tmp/[12]
  compat/simple-ipc/ipc-unix-socket.c
  run-command.c

The "compat/" file only talks about the macro in the comment,
and is not broken.

We could fix this by conditionally including "alloc.h" when
`NO_PTHREADS` is defined.  But we have relatively few examples of
conditional includes throughout the tree[^1].

Instead, include "alloc.h" unconditionally in run-command.c to allow it
to successfully compile even when NO_PTHREADS is defined.

[^1]: With `git grep -E -A1 '#if(n)?def' -- **/*.c | grep '#include' -B1`.

Reported-by: Randall S. Becker <[email-masked]>
Co-authored-by: Junio C Hamano <[email-masked]>
Signed-off-by: Junio C Hamano <[email-masked]>
Signed-off-by: Taylor Blau <[email-masked]>
---
 run-command.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/run-command.c b/run-command.c
index d4247d5fcc..60c9419866 100644
--- a/run-command.c
+++ b/run-command.c
@@ -16,6 +16,7 @@
 #include "packfile.h"
 #include "hook.h"
 #include "compat/nonblock.h"
+#include "alloc.h"

 void child_process_init(struct child_process *child)
 {
--
2.41.0.rc0.dirty