[bug #55533] .SECONDARY with % pattern

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?55533>

                 Summary: .SECONDARY with % pattern
                 Project: make
            Submitted by: None
            Submitted on: Mon 21 Jan 2019 01:38:58 AM UTC
                Severity: 3 - Normal
              Item Group: Enhancement
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: None
        Operating System: Any
           Fixed Release: None
           Triage Status: None

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Details:

GNU Make automatically deletes intermediate files that are updated in a chain
of pattern rules.

People tend to abuse .PRECIOUS to suppress the deletion of
the intermediate patterns.

In the following test code, %.yyy is an intermediate pattern.


Test code 1
-----------

%.xxx: %.yyy
[ TAB ] cp $< $@

%.yyy: %.zzz
[ TAB ] cp $< $@

.PRECIOUS: %.yyy


Result 1
--------

$ touch a.zzz
$ make a.xxx
cp a.zzz a.yyy
cp a.yyy a.xxx


It is true that it can suppress the automatic deletion of %.yyy,
but it is not the correct usage of .PRECIOUS.

The use of .PRECIOUS is quite rare because it may leave partially constructed
(i.e. corrupted but its timestamp says
it is up-to-date) files when GNU Make is interrupted.

I know why people tend to abuse .PRECIOUS;
it is because .SECONDARY does not work against % pattern.


Test code 2
-----------

%.xxx: %.yyy
[ TAB ] cp $< $@

%.yyy: %.zzz
[ TAB ] cp $< $@

.SECONDARY: %.yyy


Result 2
--------

$ rm -f a.*
$ touch a.zzz
cp a.zzz a.yyy
cp a.yyy a.xxx
rm a.yyy


The prerequisites of the .SECONDARY target must be explicit
file paths or nothing.

(.SECONDARY with no prerequisites causes all targets to be treated as
secondary.)


But, considering the motivation of .SECONDARY, I believe it would be a good
improvement to make .SECONDARY work with % pattern.





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