BUG: #4256: f2py, PyString_FromStringAndSize is undefined in Python3.

Use PyUString_FromStringAndSize defined in npy_3kcompat instead. Not
using bytes may cause some problems, but strings seem like a better
choice. As modules generated with current f2py error out, this
particular use is not common and we are free to choose.

Closes #4256.

1 files changed, 24 insertions, 0 deletions

diff --git a/numpy/f2py/tests/test_callback.py b/numpy/f2py/tests/test_callback.py
index 98a90a28c..16464140f 100644
--- a/numpy/f2py/tests/test_callback.py
+++ b/numpy/f2py/tests/test_callback.py
@@ -34,6 +34,17 @@ cf2py  intent(out) a
        external fun
        call fun(a)
        end
+
+       subroutine string_callback(callback, a)
+       external callback
+       double precision callback
+       double precision a
+       character*1 r
+cf2py  intent(out) a
+       r = 'r'
+       a = callback(r)
+       end
+
     """
 
     @dec.slow
@@ -103,6 +114,19 @@ cf2py  intent(out) a
         r = t(a.mth)
         assert_( r==9, repr(r))
 
+    def test_string_callback(self):
+
+        def callback(code):
+            if code == 'r':
+                return 0
+            else:
+                return 1
+
+        f = getattr(self.module, 'string_callback')
+        r = f(callback)
+        assert_(r == 0, repr(r))
+
+
 if __name__ == "__main__":
     import nose
     nose.runmodule()