Hi,
Here at genua, trying to build libpcap sometimes breaks in
libpcap with the following error message:
| Using $< in a non-suffix rule context is a GNUmake idiom \
| (/data/git/ehrhardt/genuos/os/mk/bsd.dep.mk:47)
The bug is in bsd.dep.mk where ${.IMPSRC} (aka $<) is used
in a context where it is not neccessarily defined by OpenBSD make.
Below is a diff to Use ${.ALLSRC:M*.y} instead of ${.IMPSRC} as
the input file for yacc.
The issue is with the rule for the grammar.h file that is generated
by yacc from grammar.c. You can easily reproduce the bug with the
following steps:
- build libpcap from scratch: cd .../src/lib/libpcap && make clean all
- remove the generated grammar.h file: rm obj*/grammar.h
- build libpcap again (incremental build): make
In normal builds this does not trigger as grammar.h is implicitly
generated by the rule for grammar.c and when make checks for
dependencies it simply finds grammar.h uptodate. However,
incremental or parallel builds might decide to make grammar.h
from grammar.y.
Now, why is this only a problem for grammar.h but not for
grammar.c? The answer to this question is burried deeply in
OpenBSD's mk files.
The snippet in bsd.dep.mk that triggers the error is a single
rule statement that generates foo.c and foo.h from foo.y with a
call to yacc -d. The rule is generated with a loop, i.e. it is not
a prefix rule. However, a prefix rule context is required for
the use of ${.IMPSRC} aka $<. For the .c file such a prefix
rule is provided by bsd.sys.mk and this rule is in scope when
make evaluates the yacc rule. However, for .h file generation
from a .y file there is no such prefix rule defined in any of
the Makefiles. Even if it were the .h suffix is missing from
.SUFFIXES and the rule would not be considered.
NOTE: The obvious way to fix this would be to use $f instead of
${.IMPSRC}. However, this does not work as $f is then missing
the path prefix and yacc won't find it if an obj directory is
used. This is probably the reason for the use of ${.IMPSRC} in
the first place.
regards Christian
diff --git a/os/mk/bsd.dep.mk b/os/mk/bsd.dep.mk
index 4bd8bf7778..77ae4f6666 100644
--- a/os/mk/bsd.dep.mk
+++ b/os/mk/bsd.dep.mk
@@ -44,7 +44,7 @@ ${i:R:S/$/.o/} ${i:R:S/$/.po/} ${i:R:S/$/.so/}
${i:R:S/$/.do/}: $i
# loop may not trigger
. for f in ${SRCS:M*.y}
${f:.y=.c} ${f:.y=.h}: $f
- ${YACC.y} -o ${f:.y=.c} ${.IMPSRC}
+ ${YACC.y} -o ${f:.y=.c} ${.ALLSRC:M*.y}
. endfor
CLEANFILES += ${SRCS:M*.y:.y=.h}
.endif
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