Re: Meson build updates

Hi,

On 2023-06-12 11:54:42 -0500, Tristan Partin wrote:
> On Fri Jun 9, 2023 at 1:36 PM CDT, Andres Freund wrote:
> > The biggest change to make them more usable would be to properly reconfigure
> > when the contents of machine file change. IIRC configure is rerun, but the
> > changes aren't taken into account.
>
> I could not reproduce this. Perhaps you were testing with an older Meson
> where that was the case
>
> # meson.build
> project('mytest')
>
> myprog = find_program('myprog')
> message(myprog.full_path())
>
> test('dummy', find_program('echo'), args: [myprog.full_path()])
>
> # file.ini
> [binaries]
> myprog = '/usr/bin/python3'
>
> # CLI
> meson setup build
> meson test -C build
> sed -i 's/python3/python2/' file.ini
> meson test -C build

It's possible that it doesn't happen in all contexts. I just reproduced the
problem I had, changing

[binaries]
llvm-config = '/usr/bin/llvm-config-13'

to

[binaries]
llvm-config = '/usr/bin/llvm-config-14'

does not change which version is used in an existing build tree, but does
change what's used in a new build tree.

Same with e.g. changing the C compiler version in a machine file. That also
only takes effect in a new tree.

This is with meson HEAD, updated earlier today.

> > In the end, I also just don't see a meaningful benefit in forcing the use of
> > machine files.
>
> I think it is best to use patterns tools want you to use.

Sometimes. I'd perhaps have a different view if we weren't migrating from
autoconf, where overwriting binaries was trivially possible...

Greetings,

Andres Freund