On Thu, Oct 12, 2023 at 04:33:54PM +0100, Peter Hull wrote: > On Thu, 12 Oct 2023 at 15:56, Sébastien Hinderer > <Sebastien.Hinderer@xxxxxxxx> wrote: > > So according to that, I expected that autoconf would call m4 with the -P > > option and looked at my /usr/bin/autoconf script but it does not seem to > > contain any occurrence of -P. But perhaps that appears in a sourced file > > or so. > You're right! Possibly it is done by 'lib/m4sugar/m4sugar.m4' in the > source code. I'll leave it to someone who knows what they're talking > about to reply! Autoconf intentionally provides m4_ prefixes as the preferred spelling for the majority of m4 builtin macros - but it does so via the m4sugar prelude that manually renames things, rather than via m4 -P. In some cases, the original builtin name is still available as well, but intentionally undocumented. Thus, in your configure.ac file, both m4_eval(...) and eval(...) will do the same actions, but only m4_eval(...) complies with the manual (and although unlikely due to back-compat reasons, some future release of autoconf could decide to make eval(...) no longer do what you want). -- Eric Blake, Principal Software Engineer Red Hat, Inc. Virtualization: qemu.org | libguestfs.org
