Issue #13415: Test in configure if unsetenv() has a return value or not.

Modules/posixmodule.c

@@ -7044,14 +7044,20 @@ static PyObject *
 posix_unsetenv(PyObject *self, PyObject *args)
 {
     char *s1;
+#ifndef HAVE_BROKEN_UNSETENV
     int err;
+#endif
 
     if (!PyArg_ParseTuple(args, "s:unsetenv", &s1))
         return NULL;
 
+#ifdef HAVE_BROKEN_UNSETENV
+    unsetenv(s1);
+#else
     err = unsetenv(s1);
     if (err)
         return posix_error();
+#endif
 
     /* Remove the key from posix_putenv_garbage;
      * this will cause it to be collected.  This has to

configure

@@ -9924,6 +9924,34 @@ $as_echo "no" >&6; }
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for broken unsetenv" >&5
+$as_echo_n "checking for broken unsetenv... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <stdlib.h>
+
+int
+main ()
+{
+int res = unsetenv("DUMMY")
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+else
+
+$as_echo "#define HAVE_BROKEN_UNSETENV 1" >>confdefs.h
+
+   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
 for ac_prog in true
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.

configure.in

@@ -2831,6 +2831,15 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
   [AC_MSG_RESULT(no)
 ])
 
+AC_MSG_CHECKING(for broken unsetenv)
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <stdlib.h>
+]], [[int res = unsetenv("DUMMY")]])],
+  [AC_MSG_RESULT(no)],
+  [AC_DEFINE(HAVE_BROKEN_UNSETENV, 1, Define if `unsetenv` does not return an int.)
+   AC_MSG_RESULT(yes)
+])
+
 dnl check for true
 AC_CHECK_PROGS(TRUE, true, /bin/true)
 

pyconfig.h.in

@@ -97,6 +97,9 @@
 /* define to 1 if your sem_getvalue is broken. */
 #undef HAVE_BROKEN_SEM_GETVALUE
 
+/* Define if `unsetenv` does not return an int. */
+#undef HAVE_BROKEN_UNSETENV
+
 /* Define this if you have the type _Bool. */
 #undef HAVE_C99_BOOL