Ned Deily <n...@acm.org> added the comment:

Thanks Garrett for reporting the problem and thank Nick for the patches.  It 
turns out the problem is more involved though the solution is similar. I've 
spent some time figuring out what went wrong here and documenting it in this 
issue so that no one else has to.  Ugh.

The relevant checkin events:

(1) (2009-07-16) r74038 changed the autoconf tests for chflags and lchflags to 
be m4a double-quoted (from '[' to '[[') to "ensure they don't get mangled".  
The test continues to use the AC_TRY_RUN macro and is working correctly.

(2) (2009-11-02) r76050 checked in a modified version of a patch from Gentoo to 
help support cross-compiling. The original patch was against a pre-r74038 
version; it wrapped the AC_TRY_RUN macro in an AC_CACHE_CHECK and a layer of 
quotes. In updating the patch for the then-current trunk (2.7), the 
significance of the r74038 change was apparently overlooked, resulting in an 
extra and faulty level of [...] quotes which end up in the configure test C 
source.  The test now gets compile errors on all Unix-y platforms but it is 
only significant on those that do support chflags and/or lchflags, i.e. BSD 
ones and OS X.

(3) (2010-01-30) The buggy test from trunk is merged into py3k (3.2) r77862, 
3.1 r77863, and 2.6 r77864.

(4) (2010-05-08) As part of Issue8510 updates to configure.in to work with 
autoconf 2.65, r80478 for py3k (3.2) and r80969 for trunk (2.7) converted the 
AC_TRY_RUN macro calls to ones using AC_RUN_IFELSE and AC_LANG_SOURCE. An extra 
level of quoting is added to preserve the existing, albeit buggy syntax.  The 
net effect is that the configure test C code generated is the same and still 
always fails with a compile error.

While I have not tested this on any BSD-like systems other than OS X, I believe 
this means that os.chflags and/or os.lchflags have been missing-in-action from 
builds on OSes where they should be supported for the following releases (i.e 
since 2009-11-02):

2.6.5
2.6.6
2.7
3.1.2
3.2a2

A side note for OS X: Apple first introduced lchflags() support in OS X 10.5.  
Since the python.org OS X installer pythons are traditionally built to an 
10.3/10.4 ABI, none of the OS X installers for the above Python releases would 
have had os.lchflags anyway (only os.chflags), except for the new 2.7 
32-bit/64-bit installer if the 2.7 test weren't otherwise broken.

The solution is to fix the buggy configure.in macros along the lines suggested 
by Nick.  I have created and tested three new patches to do this:

    issue8746-py3k.patch    for py3k (3.2a2+)
    issue8746-27.patch      for release-27-maint (2.7+)
    issue8746-31.patch      for release-31-maint (3.1.2+)

A variant of the 3.1 patch should apply to release-26-maint (2.6.6+) however 
2.6 is now in security-fix-only mode.

In each case, the patch only modifies configure.in.  It is necessary to run 
autoreconf after applying and before checkin.  A simple test of the fix is to 
do ./configure before and after:

    $ rm -f config.log config.status
    $ ./configure
    $ grep "expected identifier or '(' before " config.log
    conftest.c:191: error: expected identifier or '(' before '[' token
    conftest.c:200: error: expected identifier or '(' before ']' token
    conftest.c:191: error: expected identifier or '(' before '[' token
    conftest.c:200: error: expected identifier or '(' before ']' token
    $ patch <issue8746-[...].patch
    $ autoreconf
    $ rm -f config.log config.status
    $ ./configure
    $ grep "expected identifier or '(' before " config.log
    $

Note that I have not attempted any cross-compiling testing either with or 
without the patches.

----------
nosy: +doko, gregory.p.smith
priority: normal -> release blocker
stage: unit test needed -> patch review
title: *chflags detection broken on FreeBSD 9-CURRENT -> os.chflags() and 
os.lchflags() are not built when they should be be
Added file: http://bugs.python.org/file18837/issue8746-py3k.patch

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