BUG: linalg: norm fails on longdouble, signed int

This fixes the following bug with longdouble:

>>> x = np.arange(10, dtype=np.longdouble)
>>> np.linalg.norm(x, ord=3)
Traceback (most recent call last):
  File "<ipython-input-5-7ee53a8ac142>", line 1, in <module>
    np.linalg.norm(x, ord=3)
  File "/tmp/v/lib/python2.7/site-packages/numpy/linalg/linalg.py", line 2090, in norm
    return add.reduce(absx**ord, axis=axis)**(1.0/ord)
UnboundLocalError: local variable 'absx' referenced before assignment

As well as the handling of minimal values for signed integers:

>>> x = np.array([-2**31], dtype=np.int32)
>>> np.linalg.norm(x, ord=3)
/tmp/v/lib/python2.7/site-packages/numpy/linalg/linalg.py:2090: RuntimeWarning: invalid value encountered in double_scalars
  return add.reduce(absx**ord, axis=axis)**(1.0/ord)
nan

1 files changed, 12 insertions, 0 deletions

diff --git a/numpy/linalg/tests/test_linalg.py b/numpy/linalg/tests/test_linalg.py
index dd4cbcc4f..feb4c8224 100644
--- a/numpy/linalg/tests/test_linalg.py
+++ b/numpy/linalg/tests/test_linalg.py
@@ -909,6 +909,18 @@ class _TestNorm(object):
         assert_raises(ValueError, norm, B, None, (2, 3))
         assert_raises(ValueError, norm, B, None, (0, 1, 2))
 
+    def test_longdouble_norm(self):
+        # Non-regression test: p-norm of longdouble would previously raise
+        # UnboundLocalError.
+        x = np.arange(10, dtype=np.longdouble)
+        old_assert_almost_equal(norm(x, ord=3), 12.65, decimal=2)
+
+    def test_intmin(self):
+        # Non-regression test: p-norm of signed integer would previously do
+        # float cast and abs in the wrong order.
+        x = np.array([-2 ** 31], dtype=np.int32)
+        old_assert_almost_equal(norm(x, ord=3), 2 ** 31, decimal=5)
+
 
 class TestNormDouble(_TestNorm):
     dt = np.double