Re: Multiple rules for same target: what is the order of prerequisites in $^ and what does $< expand to?

[Renaud Pacalet]

On 9/27/23 21:39, Philip Guenther wrote:
> On Wed, Sep 27, 2023 at 7:52 AM Renaud Pacalet <renaud.pacalet@telecom-paris.fr 
> <mailto:renaud.pacalet@telecom-paris.fr>> wrote:
>
>     On 9/27/23 16:32, Bahman Movaqar wrote:
>      > On Wed, 2023-09-27 at 12:16 +0200, Renaud Pacalet wrote:
>      >
>      >> 3. Ignore all other implicit rules (which seems to contradict 4.11).
>      >
>      > Make only ignores the implicit rules for which there are
>      > explicit/static equivalents.
>
>
> Per 10.1 "Using Implicit Rules", make will only use an implicit rule for a 
> target if there isn't an explicit rule with a recipe.  If a target has an explicit rule 
> with a recipe, then make won't bother looking for implicit rules and so won't use them to 
> add more prerequisites.
>
> Note that there are additional requirements on what implicit rules will be used 
> even when they are considered: if they have a prerequisite that doesn't exist 
> and make doesn't see how to build, then it'll ignore the rule.
>
>     Thanks for your answer, Bahman. Not sure what "equivalent" means but with 
> the following Makefile:
>
>     %.a: %.b
>
>     a.a: a.c
>           echo $^
>
>
> a.a has an explicit rule with a recipe so the %.a:%.b rule has no effect on the 
> a.a target.

Thanks a lot Philip. This is in line with my own conclusions. I guess my 
algorithm is thus probably correct. Note that the findings of Bahman 
(target-specific variables are taken into accounts even if declared in a 
pattern rule while an explicit rule with recipe exists) complicate things. I 
will continue my experiments and, if I find a way to explain all this clearly 
enough, I'll submit a proposal of improvement for 4.11 which I find misleading.

Best regards,

Renaud.