Re: "make -jN" requires mechanical changes to a Makefile [SOLVED]

[Henrik Carlqvist]

On Sun, 13 Sep 2020 20:07:27 +0100
Bruno Haible wrote:
> Continuing this thread from May 2019
> <https://lists.gnu.org/archive/html/bug-make/2019-05/msg00022.html>:
> The problem was:
> 
>   How can a rule that generates multiple files be formulated so
>   that it works with parallel make?
> 
> For example, a rule that invokes bison, or a rule that invokes
> a different Makefile. For simplicity, here, use a rule that
> creates 4 files copy1, copy2, copy3, copy4.
> 
> ===========================================
> all : copy1 copy2 copy3 copy4
> 
> copy1 copy2 copy3 copy4: Makefile
>       install -c -m 644 Makefile copy1
>       install -c -m 644 Makefile copy2
>       install -c -m 644 Makefile copy3
>       install -c -m 644 Makefile copy4
> ===========================================

I would say there are two obvious solutions to make this work with parallel
make:


1) Allow the targets to be tuilt in paralllel:
===========================================
all : copy1 copy2 copy3 copy4
 
copy1 copy2 copy3 copy4: Makefile
        install -c -m 644 Makefile $@
===========================================

However, this solution 1 will not work for a single command that generates
multiple files, so we might need a solution 2:

2) Don't mention some of the extra targets:
===========================================
all : copy1
 
copy1: Makefile
        install -c -m 644 Makefile copy1
        install -c -m 644 Makefile copy2
        install -c -m 644 Makefile copy3
        install -c -m 644 Makefile copy4
===========================================

regards Henrik