Subject: Re: [PATCH] Makefile: detect errors in running spatch

From: René Scharfe <[email-masked]>
Date: Fri, 10 Mar 2017 18:03:47 +0100

Am 10.03.2017 um 09:31 schrieb Jeff King:
> The "make coccicheck" target runs spatch against each source
> file. But it does so in a for loop, so "make" never sees the
> exit code of spatch. Worse, it redirects stderr to a log
> file, so the user has no indication of any failure. And then
> to top it all off, because we touched the patch file's
> mtime, make will refuse to repeat the command because it
> think the target is up-to-date.
>
> So for example:
>
>   $ make coccicheck SPATCH=does-not-exist
>       SPATCH contrib/coccinelle/free.cocci
>       SPATCH contrib/coccinelle/qsort.cocci
>       SPATCH contrib/coccinelle/xstrdup_or_null.cocci
>       SPATCH contrib/coccinelle/swap.cocci
>       SPATCH contrib/coccinelle/strbuf.cocci
>       SPATCH contrib/coccinelle/object_id.cocci
>       SPATCH contrib/coccinelle/array.cocci
>   $ make coccicheck SPATCH=does-not-exist
>   make: Nothing to be done for 'coccicheck'.
>
> With this patch, you get:
>
>   $ make coccicheck SPATCH=does-not-exist
>        SPATCH contrib/coccinelle/free.cocci
>   /bin/sh: 4: does-not-exist: not found
>   Makefile:2338: recipe for target 'contrib/coccinelle/free.cocci.patch' failed
>   make: *** [contrib/coccinelle/free.cocci.patch] Error 1

That's nice.  The current version is just a contraption that does the 
bare minimum of work.

> It also dumps the log on failure, so any errors from spatch
> itself (like syntax errors in our .cocci files) will be seen
> by the user.
>
> Signed-off-by: Jeff King <[email-masked]>
> ---
> This shell code is getting a bit unwieldy to stick inside the Makefile,
> with all the line continuation and $-escaping.  It might be worth moving
> it into a helper script.

There is one for the kernel 
(https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/scripts/coccicheck). 
  It's quite big, though.

> It also doesn't help that shells are awkward at passing status out of a
> for-loop. I think the most "make-ish" way of doing this would actually
> be to lose the for loop and have a per-cocci-per-source target.
>
> I don't know if that would make the patches harder to apply. The results
> aren't full patches, so I assume you usually do some kind of munging on
> them?

They work with patch -p0.

We can get rid of the loop by using the spatch options --use-gitgrep and 
--dir.  I can't find the former one in the docs, though, so I'm not sure 
if it only works with certain versions or what exactly it is even doing. 
  It seems to have the side effect of producing git-style patches 
(applicable with patch -p1) at least.

> I resorted to:
>
>   make coccicheck SPATCH='spatch --in-place'

Using SPATCH_FLAGS for adding an option in such case would be a bit simpler.

>  Makefile | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 9ec6065cc..d97633892 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -2336,9 +2336,17 @@ check: common-cmds.h
>  C_SOURCES = $(patsubst %.o,%.c,$(C_OBJ))
>  %.cocci.patch: %.cocci $(C_SOURCES)
>  	@echo '    ' SPATCH $<; \
> +	ret=0; \
>  	for f in $(C_SOURCES); do \
> -		$(SPATCH) --sp-file $< $$f $(SPATCH_FLAGS); \
> -	done >$@ 2>$@.log; \
> +		$(SPATCH) --sp-file $< $$f $(SPATCH_FLAGS) || \
> +			{ ret=$$?; break; }; \
> +	done >$@+ 2>$@.log; \
> +	if test $$ret != 0; \
> +	then \
> +		cat $@.log; \
> +		exit 1; \
> +	fi; \
> +	mv $@+ $@; \
>  	if test -s $@; \
>  	then \
>  		echo '    ' SPATCH result: $@; \
>