Re: Parallel build issue with bison 3.4.1 and make 3.81

[Akim Demaille]

Hi Thomas,

I don't think the previous commit did address your issue.  The following
one should.  Could you please test it?  I could not reproduce your problem,
so I can't tell if it actually fixes it for you.  I need feedback.

You may try these tarballs if trying a patch is inconvenient.

https://www.lrde.epita.fr/~akim/private/bison/bison-3.4.1.62-e7be.tar.gz
https://www.lrde.epita.fr/~akim/private/bison/bison-3.4.1.62-e7be.tar.xz

Cheers!


commit e7be4e9ffe38ffa90e5fde653378c219e1e0491a
Author: Akim Demaille <address@hidden>
Date:   Sat Aug 3 18:57:24 2019 +0200

    examples: fix missing dependencies
    
    Reported by Thomas Petazzoni.
    https://lists.gnu.org/archive/html/bug-bison/2019-08/msg00000.html
    
    * examples/c/reccalc/local.mk: Complete dependencies, including for
    earlier versions of Automake (for sake of our CI, on top of Ubuntu
    Xenial, which features only Automake 1.15).
    (%D%/scan.c %D%/scan.h): Upgrade to the full version provided in
    Automake's documentation.

diff --git a/THANKS b/THANKS
index 14a26d76..5ee4b29a 100644
--- a/THANKS
+++ b/THANKS
@@ -171,6 +171,7 @@ Sum Wu                    address@hidden
 Théophile Ranquet         address@hidden
 Thiru Ramakrishnan        address@hidden
 Thomas Jahns              address@hidden
+Thomas Petazzoni          address@hidden
 Tim Josling               address@hidden
 Tim Landscheidt           address@hidden
 Tim Van Holder            address@hidden
diff --git a/configure.ac b/configure.ac
index a9dad57c..dd94bc22 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,6 +36,9 @@ AC_CONFIG_MACRO_DIR([m4])
 
 # We use Automake 1.14's %D% and %C%.
 #
+# When we move to Automake 1.16, simplify examples/c/reccalc/local.mk.
+# Our CI runs on Xenial, which has only Automake 1.15.
+#
 # We want gnits strictness only when rolling a stable release.  For
 # release candidates, we use version strings like 2.4.3_rc1, but gnits
 # doesn't like that, so we let the underscore disable gnits.  Between
diff --git a/examples/c/reccalc/local.mk b/examples/c/reccalc/local.mk
index bb64b214..0ff5abed 100644
--- a/examples/c/reccalc/local.mk
+++ b/examples/c/reccalc/local.mk
@@ -36,16 +36,40 @@ endif FLEX_WORKS
 # additional dependency.
 DASH = -
 %D%/reccalc$(DASH)parse.o: %D%/scan.h
+# Tell Make scan.o depends on parse.h, except that Make sees only
+# parse.c, not parse.h.  We can't use BUILT_SOURCES to this end, since
+# we use the built bison.
+%D%/reccalc$(DASH)scan.o: %D%/parse.c
 
+# Likewise, but for Automake before 1.16.
+%D%/examples_c_reccalc_reccalc$(DASH)parse.o: %D%/scan.h
+%D%/examples_c_reccalc_reccalc$(DASH)scan.o: %D%/parse.c
+
+## See "info automake 'Multiple Outputs'" for this rule.
 %D%/scan.c %D%/scan.h: %D%/scan.stamp
-       @test -f $@ || rm -f %D%/scan.stamp
-       @test -f $@ || $(MAKE) $(AM_MAKEFLAGS) %D%/scan.stamp
+## Recover from the removal of $@
+       @if test -f $@; then :; else \
+         trap 'rm -rf %D%/scan.lock %D%/scan.stamp' 1 2 13 15; \
+## mkdir is a portable test-and-set
+         if mkdir %D%/scan.lock 2>/dev/null; then \
+## This code is being executed by the first process.
+           rm -f %D%/scan.stamp; \
+           $(MAKE) $(AM_MAKEFLAGS) %D%/scan.stamp; \
+           result=$$?; rm -rf %D%/scan.lock; exit $$result; \
+         else \
+## This code is being executed by the follower processes.
+## Wait until the first process is done.
+           while test -d %D%/scan.lock; do sleep 1; done; \
+## Succeed if and only if the first process succeeded.
+           test -f %D%/scan.stamp; \
+         fi; \
+       fi
 
 %D%/scan.stamp: %D%/scan.l
        $(AM_V_LEX)rm -f $@ $@.tmp
        $(AM_V_at)$(MKDIR_P) %D%
        $(AM_V_at)touch $@.tmp
-       $(AM_V_at)$(LEX) -o%D%/scan.c --header-file=%D%/scan.h 
$(srcdir)/%D%/scan.l
+       $(AM_V_at)$(LEX) $(AM_LFLAGS) $(LFLAGS) -o%D%/scan.c 
--header-file=%D%/scan.h $(srcdir)/%D%/scan.l
        $(AM_V_at)mv $@.tmp $@