Re: dummy prerequisites and "make clean"

[Ben Pfaff]

On Fri, Nov 20, 2020 at 12:36 AM John Darrington
<john@darrington.wattle.id.au> wrote:
>
> On Thu, Nov 19, 2020 at 10:31:28PM -0800, Ben Pfaff wrote:
>      When I type "make clean", the first thing that happens is that gnulib
>      gets built. This seems to be caused by commit 49501a8888003350 "Add
>      default to generate prerequisistes for any rule", which always build
>      libgl, even if the target is "clean".
>> It should only do that if libgl is not up to date.

The "clean" target is actually completely broken. If you run "make clean"
from a fresh worktree, what happens is this:
  - libgl gets built
  - libgl gets cleaned
  - libgl gets built again (!)
And, thus, the "clean" doesn't actually work. It does not clean the build
tree.

> Yes.  Before this commit, attempting to run many targets from a clean tarball
> without first running "make" (from memory, I think "make check", "make doc" 
> and
> "make install" were just some of those affected), resulted in wierd failures 
> after
> about five minutes half way through the process.

That's pretty well-understood behavior that is actually documented in the
Automake manual (under "Built Sources"). If it's annoying, then we can
work on eliminating the use of BUILT_SOURCES. (It would be harder to
fix libgl.)