Date: Fri, 11 Aug 95 18:08 CDT From: gordon@sneaky.lonestar.org To: FreeBSD-gnats-submit@freebsd.org Subject: bin/675: make does unnecessary rebuilds starting with FreeBSD 2.0R Message-ID: <m0sh3Bs-0001hRC@hammy.lonestar.org> Resent-Message-ID: <199508120150.SAA05687@freefall.FreeBSD.org>
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>Number: 675
>Category: bin
>Synopsis: make does unnecessary rebuilds
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Aug 11 18:50:01 PDT 1995
>Last-Modified:
>Originator: Gordon Burditt
>Organization:
what organization?
>Release: FreeBSD 2.0-BUILT-19950603 i386
>Environment:
FreeBSD 2.0.5R
>Description:
When make encounters a rule that may or may not update the
target, it considers the target modified whether it actually
is or not, and forces recompiles of everything that depends
on that target. This behavior is new starting with 2.0;
1.1R and 1.1.5.1R forced recompiles of everything that depends
on that target only if it was actually modified.
The makefile attached below builds a program, and the only
thing unusual about it is the use of cproto to automatically
build a prototype file included by all source files. The
header file is only modified if the prototypes actually
change. Recompilation of everything is needed only if
proto.h is touched.
Is there any way to get the behavior I want?
>How-To-Repeat:
Create an empty directory (preferably on a non-NFS filesystem)
with the attached Makefile, a.c, b.c, and c.c files in it.
Do a make, which will build the program. Touch c.c. Do
another make. Recompiling c.c is necessary, but recompiling
a.c and b.c is not. 2.0R and 2.0.5R make recompile everything;
1.1R and 1.1.5.1R recompile only c.c.
Makefile:
_______________________________
all: prog
prog: a.o b.o c.o
$(CC) -o prog a.o b.o c.o
proto.h: proto.tmp
-if cmp proto.tmp proto.h; then : ; else cp proto.tmp proto.h; fi
proto.tmp: a.c b.c c.c
cproto a.c b.c c.c > proto.tmp
# This would normally go in .depend
a.o: proto.h a.c
b.o: proto.h b.c
c.o: proto.h c.c
_______________________________
a.c:
_______________________________
# include "proto.h"
void a(void) { puts("hello"); }
_______________________________
b.c:
_______________________________
# include "proto.h"
void b(void) { puts("world"); }
_______________________________
c.c:
_______________________________
# include "proto.h"
int main(void) { a(); b(); return 0; }
_______________________________
Note: if you don't have cproto, for the purpose of this test you
can replace it with "grep frobnicate".
Comments in the make source near "RECHECK" in compat.c and make.c
discuss this problem. The obvious fix is to define RECHECK.
The trouble is, RECHECK already IS defined and it still doesn't work.
>Fix:
>Audit-Trail:
>Unformatted:
help
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