Pattern matching for static pattern rules

[Alex Dehnert]

I was running into some behavior that surprised me when using static 
pattern rules with files in a subdirectory.

A fairly minimal case:
$ mkdir foo && echo foo/bar > foo/text.bar

$ cat Makefile
all : foo/text.bar.sha1 foo/text.bar.md5

text.%.sha1 : text.%
        sha1sum "$<" > "$@"

foo/text.bar.md5 : text.%.md5 : text.%
        md5sum "$<" /dev/null > "$@"

$ make
Makefile:7: target `foo/text.bar.md5' doesn't match the target pattern
sha1sum "foo/text.bar" > "foo/text.bar.sha1"
md5sum "" /dev/null > "foo/text.bar.md5"
md5sum: : No such file or directory
make: *** [foo/text.bar.md5] Error 1

With (implicit) pattern rules, "When the target pattern does not contain a 
slash (and it usually does not), directory names in the file names are 
removed from the file name before it is compared with the target prefix 
and suffix."[1] With static pattern rules, this doesn't seem to be the 
case. I'm not sure whether this is intentional or not. The documentation 
seems to suggest that static pattern rules and implicit pattern rules 
should behave basically equivalently (with respect to pattern-matching 
file names, at least), claiming that "A static pattern rule has much in 
common with an implicit rule defined as a pattern rule (see Defining and 
Redefining Pattern Rules). Both have a pattern for the target and patterns 
for constructing the names of prerequisites. The difference is in how make 
decides when the rule applies."[2]

It seems like either this is a bug in the code, or something that should 
be clarified in the documentation as a difference between the two rule 
types.

(I'd imagine this may not have been noticed because in the (common?) case 
that the pattern is "%something", it doesn't mattern whether the directory 
is removed first, then the pattern is matched, and finally the directory 
re-added; or the match is done against the full path. Unfortunately, for 
my actual case, filenames have a common prefix, not a common suffix.)

Thanks,
Alex

[1] 
https://www.gnu.org/software/make/manual/html_node/Pattern-Match.html#Pattern-Match
[2] 
https://www.gnu.org/software/make/manual/html_node/Static-versus-Implicit.html#Static-versus-Implicit