Surprising pattern matching and .EXTRA_PREREQS behaviours

[Daniel Gerber]

Hi,

I've found these surprising behaviours (in make v4.3). Are there any chance
to see them changed?

1. Second expansion is not applied to .EXTRA_PREREQS

2. Setting .EXTRA_PREREQS as pattern-specific variable is not supported

3. In setting pattern-specific variables, patterns with no slash are not
matched by first removing dir names. (As one finds out iff reading the doc
carefully — "The directories are ignored only for the purpose of finding
an implicit rule to use, not in the application of that rule.") See a
previous surprised user here
<https://lists.gnu.org/archive/html/bug-make/2017-08/msg00016.html>.


As a consequence, I've no good solution to the following two problems.

1. How to add a prerequisite to all targets matching some pattern — in
particular, their parent directory? This does not work as hoped:

.SECONDEXPANSION:
%.ext: .EXTRA_PREREQS = | $$(@D)/
%/: ; mkdir -p $@


2. How to set a variable for all targets matching <dirs>/prefix_<stem>?

%_suffix: var = OK this matches target dir/stem_suffix

prefix_%: var = NO this won't match dir/prefix_stem


For context, I thought one could write a library of pattern rules of the
form <prefix_dirs>/rule_type_<suffix_id> and deriving various parameters
from prefix dirs and suffix id. I guess I'll have to rewrite it as
<prefix_dirs>/<prefix_id>_rule_type or use global variables, and make
parent dirs explicitly.


Thanks for your comments,

Daniel Gerber