[PATCH] Makefile: detect errors in running spatch

From: Jeff King <peff@peff.net>
Date: Mar 10, 2017, 08:31 UTC
Message-ID: <20170310083117.cbflqx7zbe4s7cqv@sigill.intra.peff.net>

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

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 <peff@peff.net>
---
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.

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? I resorted to:

  make coccicheck SPATCH='spatch --in-place'

 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: $@; \

-- 
2.12.0.450.gd7e60cc16