[bug #58556] Make is confused by a target named ".o" and neither emptying .SUFFIXES nor MAKEFLAGS=r can prevent this

[Rossen Mikhov]

Follow-up Comment #4, bug #58556 (project make):

It is not ineffective! Did you try it?

touch foo.c
printf MAKEFLAGS=r | make - foo.o
make: *** No rule to make target 'foo.o'.  Stop.
make foo.o
cc    -c -o foo.o foo.c

The builtin rule is suppressed by MAKEFLAGS, as expected.
This doesn't work ONLY when the target is named exactly ".o".

But as I said, the point here is not whether MAKEFLAGS=r is effective in
principle or not; it is effective whenever it should be and that works fine.
If you insist, you can ignore the part of this report that refers to MAKEFLAGS
at all, and the bug is still there.

Especially the following point:

> - There are no prerequisites in the empty directory, so an implicit rule
with prerequisites should not be invoked at all, whether the rule is builtin
or is actually defined in the main makefile. Neither "make foo" nor "make
foo.o" tries to invoke "cc" in any way, only "make .o" does. 

Matching an implicit rule when its prerequisites are non-existing is in direct
contradiction to the manual section 10.8 "Implicit Rule Search Algorithm". So
there seems to be an internal rule with *no prerequisites* for a file named
".o" (which I identified as an explicit, not implicit rule, from the "make -d"
output). This is the essence of what I am reporting. Everything else is
diagnostics, things I tried in order to investigate the circumstances where
this manifests in order to be helpful to the people looking into this. Thank
you for bearing with me.


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