If you put the following line in Modules/Setup:

  SELF=$(SELF)

and then type "make", sysconfig.py's parse_makefile
function gets into an infinite loop.  Attached is a
backtrace after typing Control-C during the infinite loop.

Here is the (honest?) mistake that I made in Setup that
triggered this (Notice the extra "\"):

PURE_STUBLIBS=-lpurify_stubs -lquantify_stubs \
	-L/foo/lib \
	-R/foo/lib \
pure puremodule.c $(WHICH_PURE_PRODUCTS) $(PURE_INCLS)
$(PURE_STUBLIBS)

This is still applies for trunk.

I've added the following lines to Makefile (in the top level directory).

SELF=$(SELFA)
SELFA=$(SELF)

Running make then hangs.
I'm attaching a patch, which fixes this issue (against trunk). Running
make now prints:

~/python-trunk/ make                                             
ralf@rat64 ok
sysconfig.py: warning: could not resolve names from makefile (recursive
definition?): {'SELFA': '$(SELF)', 'SELF': '$(SELFA)'}
running build
running build_ext
INFO: Can't locate Tcl/Tk libs and/or headers

Failed to find the necessary bits to build these modules:
_bsddb            _tkinter          bsddb185       
dbm               dl                gdbm           
imageop           sunaudiodev                      
To find the necessary bits, look in setup.py in detect_modules() for the
module's name.

running build_scripts

Is a "print" really the right way to emit this warning?

distutils.extension has:

            if warnings is not None:
                warnings.warn(msg)
            else:
                sys.stderr.write(msg + '\n')

Thank you for the patch. Review:

1) Why not raise an exception? A recursive variable definition is an error. Tarek, is this behavior change OK?

2) Does this apply to the new top-level sysconfig module and/or distutils.sysconfig?

3) I’d use a more specific name for the test method: test_bogus_variable instead of test_parse_makefile. I would also add a test for SELF=$(SELF) (currently there is only a test for cyclic definition, not recursive).

4) os.unlink(makefile) is not guaranteed to run, for example if the test is stopped or crashes. Put self.addCleanup(os.unlink, makefile) after the mkstemp call instead.

5) I didn’t know there was no “if __name__ == '__main__'” block in this test file, nice catch. There is no need for the intermediate test_main function, though: unittest.main() should be enough.

6) Minor style issues: You can use textwrap.dedent to keep the file contents in the os.write call indented; s/you're/your/; no need to del fd; put spaces around operators (here == and =); don’t add tree blank lines. See PEP 8 for more info.