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ignore specific file in VPATH/vpath

From: Jannick
Subject: ignore specific file in VPATH/vpath
Date: Wed, 9 May 2018 14:30:15 +0200


I am having an issue with the make vpath/VPATH configuration where make
should ignore a specific existing file in vpath/VPATH. Here my case for
which any input from you is highly appreciated:

Cd'ed to the folder 'build', the objective is to build prog with the source
files prog.c and parse.y, both sitting in 'src':

|       makefile
        parse.c <<< disregard for a build in folder 'build'

The nasty thing is src/parse.c which unfortunately does exist, but should be
ignored for our project, since build/parse.c should be separately build
(from parse.y) and used instead.

Currently, I am not able - in an elegant way - to avoid that make uses
src/parse.c, unless make -B. The following makefile does the job, but it is
not very elegant to set up a vpath statement for each .c source file (this
is just a tiny example, in real life there might be many of those required).

$ cat makefile

src_dir                 = ../src
prog:                   prog.o parse.o
%.c:                    %.y
                        bison -o $@ $<

# vpath statement for each .c source file, not very elegant
vpath   %.y             $(src_dir)
vpath   prog.c          $(src_dir)

1 - Using VPATH = $(src_dir) instead of the vpath block does not work, since
then make uses src/parse.c unless make -B. 
2 - Another solution could be to copy the source files to build and take it
from there.
3 - My question: Is there any (easy) tweak to the makefile above (without
the given vpath block) to make that happen - or should be a copy to build
folder & compile method applied or something else I was not thinking of? 

Separately, an additional note: make's YACC built-in recipe

%.c: %.y
#  recipe to execute (built-in):
        $(YACC.y) $< 
         mv -f $@

appears to assume that YACC/bison's output file name defaults to
However, it is $*.tab.c for bison >= 3.0 (at least). Would that be worth an
enhancement to make to update to the new built-in recipe? Here I am not sure
which versions of yacc are out there and what their output files are named.

Many thanks for any input!


- GNU Make 4.2.1; Built for i686-pc-cygwin
- bison (GNU Bison) 3.0.4

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