Fix crash during perl's shutdown when env variables were modified by …

…Python

When perl is configured without -Accflags='-DPERL_USE_SAFE_PUTENV' it modifies
environment variables directly without going through the C library. During
shutdown of the interpreter it will then free() the environment variable strings.

Python uses its own allocator for strings so a free() on one of those will
explode with for example:
*** glibc detected *** /build/toolchain/lin32/perl-5.10.0/bin/perl:
free(): invalid pointer: 0x0da50904 ***

Perl can be forced to use putenv() to set environment variables by compiling
with -DPERL_USE_SAFE_PUTENV or at runtime by setting PL_use_safe_putenv to a
non-zero value. It will then not try to free() the environment strings either.

So we set PL_use_safe_putenv to avoid the free(). The downside is that
environment variables may be leaked on systems without a safe putenv(). But
that's probably still better than the crash.

Fixes GH #7 and #9

Python.xs

@@ -66,6 +66,7 @@ void do_pyinit() {
 MODULE = Inline::Python   PACKAGE = Inline::Python
 
 BOOT:
+PL_use_safe_putenv = 1;
 py_true  = perl_get_sv("Inline::Python::Boolean::true",  FALSE);
 py_false = perl_get_sv("Inline::Python::Boolean::false", FALSE);
 #ifdef CREATE_PYTHON

t/34env.t

@@ -0,0 +1,8 @@
+use Test::More;
+use Inline Python => <<PYTHON;
+import os
+os.environ["TEST_VARIABLE"] = "BOB"
+PYTHON
+ok(1, 'survived Python setting an env variable');
+done_testing;
+# might explode during cleanup but the test harness will catch that