[bug #63125] Automatic variables in Secondary Expansion don't work as documented

[Riccardo P. Bestetti]

URL:
  <https://savannah.gnu.org/bugs/?63125>

                 Summary: Automatic variables in Secondary Expansion don't
work as documented
                 Project: make
               Submitter: vmsh0
               Submitted: Wed 28 Sep 2022 08:24:02 PM UTC
                Severity: 3 - Normal
              Item Group: Bug
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: 4.3
        Operating System: POSIX-Based
           Fixed Release: None
           Triage Status: None


    _______________________________________________________

Follow-up Comments:


-------------------------------------------------------
Date: Wed 28 Sep 2022 08:24:02 PM UTC By: Riccardo P. Bestetti <vmsh0>
The GNU Make manual on Secondary Expansion[1] reports in section "Secondary
Expansion of Explicit Rules":

"The $$< variable evaluates to the first prerequisite in the first rule for
this target."

As such, with the Makefile reported at the end of this submission (Makefile),
I would expect the output "foo.1 foo.2 foo.1" or "foo.2 foo.1 foo.1". Instead,
I get the output "foo.1 foo.2".

Note that this doesn't only work unexpectedly for the $$< second expansion
automatic variable, but also for the other automatic variables, which also
expand to the empty string.

See Exhibit 1 and Exhibit 2, both at the end of this submission, to observe
that the unexpected behaviour doesn't present e.g. in Make 3.81.

[1]:
https://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html

----
Makefile

.SECONDEXPANSION:

foo: foo.1
foo: foo.2 $$<
        @echo $^

foo.%:
        @echo -n

----
Exhibit 1: Make 4.3

$ ls -lah
total 12K
drwxr-xr-x  2 random random 4.0K Sep 28 22:13 .
drwxr-xr-x 17 random random 4.0K Sep 28 21:50 ..
-rw-r--r--  1 random random   73 Sep 28 22:13 Makefile

$ md5sum Makefile
c21dd3f5b109590fa5112b50afc986d6  Makefile

$ make --version
GNU Make 4.3
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ make
foo.2 foo.1

----
Exhibit 2: Make 3.81

$ ls -lah
total 12K
drwxr-xr-x 2 root root 4.0K Sep 28 16:14 .
drwx------ 1 1000 1000 4.0K Sep 28 16:14 ..
-rw-r--r-- 1 root root   73 Sep 28 16:11 Makefile

$ md5sum Makefile
c21dd3f5b109590fa5112b50afc986d6  Makefile

$ make --version
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for x86_64-pc-linux-gnu
$ make
foo.2 foo.1 foo.1







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