NetBSD Problem Report #58229

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Date: Mon,  6 May 2024 19:53:54 +0000 (UTC)
From: thorpej@me.com
Reply-To: thorpej@me.com
To: gnats-bugs@NetBSD.org
Subject: BSD make and GNU make differ in $< and $> handling in an annoying way
X-Send-Pr-Version: www-1.0

>Number:         58229
>Category:       toolchain
>Synopsis:       BSD make and GNU make differ in $< and $> handling in an annoying way
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon May 06 19:55:00 +0000 2024
>Last-Modified:  Wed May 08 19:45:01 +0000 2024
>Originator:     Jason Thorpe
>Release:        NetBSD 10.99.10
>Organization:
Just the BASICs
>Environment:
NetBSD the-ripe-vessel 10.99.10 NetBSD 10.99.10 (GENERIC) #68: Fri Nov 17 14:40:27 PST 2023  thorpej@the-ripe-vessel:/space/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
For the following Makefile snippet behaves differently in GNU make vs BSD make:

 ---- snip ----

OBJS=           tbvm.o
CLEANFILES=     $(OBJS) tbvm_program.h libtbvm.a
CFLAGS=         -Os -g -Wall -Wformat

all: libtbvm.a

tbvm.o: Makefile tbvm.c tbvm.h tbvm_opcodes.h tbvm_program.h

tbvm_program.h: tbvm_program.asm
        ../tbasm/tbasm -H $<

libtbvm.a: $(OBJS)
        rm -f $@
        ar -r $@ $(OBJS)
        ranlib $@

clean:
        -rm -f $(CLEANFILES)

 ---- snip ----

BSD make:

the-ripe-vessel:thorpej 51$ make tbvm_program.h
../tbasm/tbasm -H 
usage: tbasm [-o output.bin] input.asm
usage: tbasm -H[output.h] input.asm
*** Error code 1

Stop.
make: stopped in /home/thorpej/Github/thorpej/JTTB/tbvm
the-ripe-vessel:thorpej 52$ 


GNU make:

the-ripe-vessel:thorpej 52$ gmake tbvm_program.h
../tbasm/tbasm -H tbvm_program.asm
parsed 388 instructions (129 labels, 220 references)
program size: 1128 bytes
the-ripe-vessel:thorpej 53$ 


$< is ${.IMPSRC} in BSD make, and the behavior is documented:

           .IMPSRC       In suffix-transformation rules, the name/path of the
                         source from which the target is to be transformed
                         (the "implied" source); also known as `<'.  It is not
                         defined in explicit rules.

...but here's the annoying part: If I change to $> (${.ALLSRC}) it works in BSD make, but then fails in GNU make:

the-ripe-vessel:thorpej 57$ gmake
../tbasm/tbasm -H 
usage: tbasm [-o output.bin] input.asm
usage: tbasm -H[output.h] input.asm
gmake: *** [Makefile:10: tbvm_program.h] Error 1
the-ripe-vessel:thorpej 58$ 

>How-To-Repeat:
See above.
>Fix:
that would be nice.

>Audit-Trail:
From: Joseph Koshy <jkoshy@netbsd.org>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: toolchain/58229: BSD make and GNU make differ in $< and $> handling
Date: Wed, 8 May 2024 20:44:22 +0100

 Does gmake support '$>'?

 For gmake v4.3 the manual (i.e., "info gmake") doesn't mention an
 automatic variable named '$>'.

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