Re: Automake's file locking

[Nick Bowler]

On 2021-02-03, Bob Friesenhahn <bfriesen@simple.dallas.tx.us> wrote:
> GNU make does have a way to declare that a target (or multiple
> targets) is not safe for parallel use.  This is done via a
> '.NOTPARALLEL: target' type declaration.

According to the manual[1], prerequisites on .NOTPARALLEL target are
ignored and this will simply disable parallel builds completely for
the entire Makefile.  I did a quick test and the manual seems to be
accurate about this.

Order-only prerequisites can be used to prevent GNU make from running
specific rules in parallel.  These are more difficult (but not impossible)
to declare in an interoperable way.

[1] https://www.gnu.org/software/make/manual/make.html#index-_002eNOTPARALLEL

Cheers,
  Nick