The C linkage is guarded by WITH_THREAD.  The 'extern "C" {' and '}' declarations should be in effect regardless of threading.

Note that the bug can only be triggered by compiling without threads, but with a C++ compiler; this is obscure enough that I don't feel strongly about backporting.

http://hg.python.org/cpython/file/0f114b855824/Python/pystate.c#l25


#ifdef WITH_THREAD
#include "pythread.h"
static PyThread_type_lock head_mutex = NULL; /* Protects interp->tstate_head */
#define HEAD_INIT() (void)(head_mutex || (head_mutex = PyThread_allocate_lock()))
#define HEAD_LOCK() PyThread_acquire_lock(head_mutex, WAIT_LOCK)
#define HEAD_UNLOCK() PyThread_release_lock(head_mutex)
 
#ifdef __cplusplus
extern "C" {
#endif

I don't think you need anyone's permission to commit such a fix :)

New changeset 5cc359804d61 by Benjamin Peterson in branch '3.2':
take linkage def outside of WITH_THREAD conditional (closes #14569)
http://hg.python.org/cpython/rev/5cc359804d61

New changeset 508ae5d27c2c by Benjamin Peterson in branch '2.7':
take linkage def outside of WITH_THREAD conditional (closes #14569)
http://hg.python.org/cpython/rev/508ae5d27c2c

On Fri, Apr 13, 2012 at 6:19 AM,
Antoine Pitrou <pitrou@free.fr> added the comment:

> I don't think you need anyone's permission to commit such a fix :)

Well, *I* would, since I don't have commit privs, and don't currently
have a C dev environment with which to test.

But I figured testing the various build conditions might be good
documentation-of-ability for someone applying to GSoC or otherwise
trying to get started. (OK, the timing wouldn't be ideal, ...)

That said, I foresee adding build-multiple-ways to the regression
tests (as opposed to a buildbot), so I'll let the next applicant come
up with something else.  :D