[bug #62936] Confusing description of chained rules in the manual

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?62936>

                 Summary: Confusing description of chained rules in the manual
                 Project: make
               Submitter: None
               Submitted: Mon 22 Aug 2022 09:05:20 AM UTC
                Severity: 3 - Normal
              Item Group: Documentation
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: 4.3
        Operating System: None
           Fixed Release: None
           Triage Status: None


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Follow-up Comments:


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Date: Mon 22 Aug 2022 09:05:20 AM UTC By: Anonymous
Trying to understand a bug in my Makefile, I consulted the manual section on
chained rules
(https://www.gnu.org/software/make/manual/html_node/Chained-Rules.html#Chained-Rules)
and found the following paragraph, which is more confusing than helpful:

> The first difference is what happens if the intermediate file
> does not exist. If an ordinary file b does not exist, and make
> considers a target that depends on b, it invariably creates b
> and then updates the target from b. But if b is an intermediate
> file, then make can leave well enough alone. It won’t bother
> updating b, or the ultimate target, unless some prerequisite
> of b is newer than that target or there is some other reason
> to update that target. 

The whole paragraph is about the case of an intermediate file that does not
exist. But then there are references to updating the file - you cannot update
a non-existing file! Also, "make can leave well enough alone" sounds more like
the description of a person having a bad day than of a deterministically
running computer program.

Unfortunately, I cannot propose a better formulation because I don't know how
Make deals with this case - I really need the manual to help me out!

Cheers,
  Konrad.







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