bug#55025: Automake should allow one to enable POSIX make behavior

[Vincent Lefevre]

On 2023-10-02 15:17:13 -0600, Karl Berry wrote:
> Sorry, I don't understand what you want Automake to do.
> 
> Right now, as far as I can tell, Automake does nothing with .POSIX. It's
> not mentioned in the manual nor, as far as I can grep, the code. Maybe
> that's the issue, and you want a leading .POSIX in your Makefile.am to
> be specially copied at the beginning of the output Makefile.in?
> (Or an option, or something.)

Yes, Automake should either detect a ".POSIX:" in the Makefile.am
file (at least if it is the first non-comment line) and place it at
the beginning of Makefile.in, or provide an option to be used with
AM_INIT_AUTOMAKE (or AUTOMAKE_OPTIONS) in order to have a ".POSIX:"
at the beginning of Makefile.in.

> But ... have you tried to run a Makefile originating from Automake with
> .POSIX in effect?  I feel doubtful that it will work, although I don't
> know it for a fact.  -k

The Makefile.am files of GNU MPFR have a ".POSIX:" target as the
first non-comment line: the shell for recipes is expected to be
run with the -e flag. So, the ".POSIX:" is necessary for GNU Make
in order to detect errors[*] (fortunately, GNU Make does not seem
to care about its position in Makefile).

[*] It is not needed for a successful build, but its absence might
yield successful builds that are actually broken.

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Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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