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

Modules/posixmodule.c

@@ -6185,18 +6185,24 @@ posix_unsetenv(PyObject *self, PyObject *args)
 {
     PyObject *os1;
     char *s1;
+#ifndef HAVE_BROKEN_UNSETENV
     int err;
+#endif
 
     if (!PyArg_ParseTuple(args, "O&:unsetenv",
                           PyUnicode_FSConverter, &os1))
         return NULL;
     s1 = PyBytes_AsString(os1);
 
+#ifdef HAVE_BROKEN_UNSETENV
+    unsetenv(s1);
+#else
     err = unsetenv(s1);
     if (err) {
         Py_DECREF(os1);
         return posix_error();
     }
+#endif
 
     /* Remove the key from posix_putenv_garbage;
      * this will cause it to be collected.  This has to

configure.in

@@ -2696,6 +2696,15 @@ 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

@@ -98,6 +98,9 @@
 /* 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