Patch by Akira Kitada.

On FreeBSD6, pthread_kill() doesn't work on the main thread before the creation
of the first thread. Create therefore a dummy thread (no-op) a startup to
initialize the pthread library.

Add also a test for this use case, test written by Charles-François Natali.

Patch by Francisco Martín Brugué.

The new wording is based on the comments in the code, which
match the actual behavior.

Locks are implemented using a mutex and a condition variable of the pthread
library on FreeBSD6. POSIX condition variables cannot be interrupted by signals
(see pthread_cond_wait manual page).

I didn't rename the variable because I can see no good reason
to break backward compatibility just to put an underscore in
the name.

Cannot test an empty environment on Windows: Windows requires at least the
SYSTEMROOT environment variable to start Python.

Cannot test an empty environment on Windows: Windows requires at least the
SYSTEMROOT environment variable to start Python.

Add a basic synchronization code between the child and the parent processes:
the child writes "ready" to stdout.

Mac OS X adds __CF_USER_TEXT_ENCODING variable to an empty environment. Fix
also the test on the Py_ENABLE_SHARED config varible: test that the variable is
present, don't check it's value.

Mac OS X adds __CF_USER_TEXT_ENCODING variable to an empty environment. Fix
also the test on the Py_ENABLE_SHARED config varible: test that the variable is
present, don't check it's value.

shared mode

Try also to get more informations about the Mac OS X failure: display the keys
of the environment, instead of just the number of variables.

Try also to get more informations about the Mac OS X failure: display the keys
of the environment, instead of just the number of variables.

environment variables, start with an empty environment.

variables, start with an empty environment.

The previous tests used time.sleep() to synchronize two processes. If the host
was too slow, the test could fail.

The new tests only use one process, but they use a subprocess to:

 - have only one thread
 - have a timeout on the blocking read (select cannot be used in the test,
   select always fail with EINTR, the kernel doesn't restart it)
 - not touch signal handling of the parent process

number of processes if negative or null.

processes if negative or null.

Use os.access(path, os.X_OK) instead of (os.stat(path).st_mode & 0o111 != 0),
and ignore the test on Windows.