Re: [PATCH] Makefile: make COMPUTE_HEADER_DEPENDENCIES=auto work with DEVOPTS=pedantic

On Wed, Sep 22 2021, Junio C Hamano wrote:

Ævar Arnfjörð Bjarmason  [off-list ref] writes:

quoted

The "COMPUTE_HEADER_DEPENDENCIES" feature added in [1] was extended to
use auto-detection in [2]. Then when -Wpedantic support was added to
DEVOPTS in [3] we started passing -Wpedantic in combination with
-Werror to the compiler here.

This broke the auto-detection, but since we'd quieted it in [4] we
didn't find out.

Are the references correct?  I am not seeing "quiet"ing in [4].  The
redirection 2>&1 to cram error messages also to $(dep_check), hence
making it impossible to match '0', was done in [2].

Yes it's incorrect, I meant [2]. I had this right in my head, just got
the references wrong somehow,thanks.

We did make the pedantic mode the default and pass both -pedantic
and -Wpedantic after [4].  Before we had only -pedantic.

*nod*

quoted

It was emitting all of this on STDERR under GCC:

    /dev/null:1: error: ISO C forbids an empty translation unit
    [-Werror=pedantic]
    cc1: note: unrecognized command-line option
    ‘-Wno-pedantic-ms-format’ may have been intended to silence
    earlier diagnostics
    cc1: all warnings being treated as errors

Let's fix that bug by maintaining a NON_DEVELOPER_CFLAGS, it's like
ALL_CFLAGS but without anything we add in config.mak.dev, and
furthermore stop redirecting STDERR to /dev/null, this means that
someone whose compiler doesn't support this will see this output, but
also this new message:

    Non-zero 1 exit with COMPUTE_HEADER_DEPENDENCIES=auto, set it to "yes" or "no" to quiet auto-detect

Hmmmmmph.  

I recentaly saw many .depend directories (not necessarily empty)
left after "make distclean". After building on one branch, I often
check out a different branch then run distclean on the new branch,
so leftover build artifacts are not necessarily a bug in our
Makefile, but the bug you found may explain it?

Yes, I'll update the commit message, the problem is that we'll empty the
dep_dirs list if we're not *currently* making them, that's a logic error
in a few places in the Makefile, i.e. conflating currently building X
with wanting to clean X.

[Will respond to the rest with a re-roll and/or in other replies in-thread]