According to a comment in line 2694 of gcc/Makefile.in, a dummy command like
@true must be added to a rule to "force gnu make to recheck modification
times.".
But the GNU make manual says that a rule without a command simply states a
dependency.
In gcc, many of those "dependency only" rules depend on a stamp. A
hack that may be used to remove the stamp itself is to use a pattern rule
where the % matches just a single character (the . for example).
Attached are three makefiles that illustrate the alternatives:
Makefile1: uses a pattern rule
Makefile2: uses a rule without a command
Makefile3: uses a rule with a dummy command (the current way)
All the three makefiles behave the same.
I will try to change gcc's makefiles and, if all goes well, submit a patch
(for 4.2).
Rafael
all: foo.c bar.h
foo%c bar%h: gen
touch foo.c
touch bar.h
all: foo.c bar.h
foo.c bar.h: s-gen
s-gen: gen
touch foo.c
touch bar.h
touch s-gen
all: foo.c bar.h
foo.c bar.h: s-gen
@true
s-gen: gen
touch foo.c
touch bar.h
touch s-gen
