From 26f359e6e8011f7547b044a680de3af992a2dfda Mon Sep 17 00:00:00 2001
From: Jeroen Demeyer <jdemeyer@cage.ugent.be>
Date: Fri, 18 Sep 2015 17:17:11 +0200
Subject: [PATCH] Fix unpickling old Matrix_mod2e_dense instances

---
 src/sage/matrix/matrix_gf2e_dense.pyx | 7 +++++++
 src/sage/matrix/matrix_space.py       | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/src/sage/matrix/matrix_gf2e_dense.pyx b/src/sage/matrix/matrix_gf2e_dense.pyx
index 46331dc373f..8e97706d80c 100644
--- a/src/sage/matrix/matrix_gf2e_dense.pyx
+++ b/src/sage/matrix/matrix_gf2e_dense.pyx
@@ -1609,6 +1609,13 @@ def unpickle_matrix_gf2e_dense_v0(Matrix_mod2_dense a, base_ring, nrows, ncols):
         True
         sage: f(*s) == A
         True
+
+    We can still unpickle pickles from before :trac:`19240`::
+
+        sage: old_pickle = 'x\x9c\x85RKo\xd3@\x10\xae\xdd$$\xdb&\xe5U\x1e-\x8f\xc2\xc9\x12RD#$\xce\xa0\xb4\x80\x07\xa2\xca\xc2\x07\x0e\xd5\xe2:\x1b\xdb\x8acg\x1c\xa7J\x85*!\xa4\x90\xe6\x07p\xe0\xc4\x01q\xe5\xc4\x19\xf5\xd0?\xc1\x81\xdf\x80\xb8q\x0b\xb3\x8eMS\xa1\x82V;;\xb3\xdf\xce\xf7\xcd\x8e\xe6\xb5j\xf7,GT;V\x1cy\x83\xf4\xe0\x9d\xb0Y\x13\xbc)\x82\x9e`\xfd\xa0\xeb\xd9m_\xf0\xbf1\xbe{\x97\xa1\xa2\x9d\xc6\xf0\x0f\x82,\x7f\x9d\xa1\xaa\x81\n\xb9m\x9c\xd7\xf4\xf1d2\x81-h\xc0#(\x03\x83\x15\xdas\xc9*\xc3\x13x\x0cu0\xd28\x97\x9e*(0\x9f\xfa\x1b\xd0\xd2\x7fH\x82\xb5\xf4\xa2@TO\xe19\x01I\xac\x136\x991\x9f\xa4\xf9&\xcd\x07i\xbe\xcb\xd4ib\t\xba\xa4\xf6\x02zIT\xd1\x8f2(u\x15\xfd\x9d<\xee@\x05V\xd3\x94E*\xb0\x0e\x0fH\xad\xa8\xbf\x97\xa0\r\x03\xfd\xf0\xb8\x1aU\xff\x92\x90\xe8?\xa5\xd6\x814_\xa5\xf9(\xcd\xafc\xe99\xe2\xd9\xa0\x06\xd4\xf5\xcf\xf2\xf2!\xbc\xd4\xdf\x90#\xc0\x8f\r\xccM\x1b\xdd\x8b\xa3\xbe\x1d\xf7#QmYv\x1cF{\xcc\x11\x81\x88<\x9b\xa71\xcf:\xce0\xaf\x9d\x96\xe3\x87a\xbb\xdf\xe5\x8e\x1f\xeeX>\xc3\x82\xb9\xb0\xe9\x05^,6=\xe17\xf1\xcc\xd0\xc0"u\xb0d\xe6wDl\xdd\x1fa)e\x8a\xbc\xc0\xe9U\xbd \x16\x8e\x88X\xc7j\x0b\x9e\x05\xc8L\xe5\x1e%.\x98\x8a5\xc4\xc5\xd9\xf7\xdd\xd0\xdf\x0b\xc2\x8eg\xf93.wZ\xb5\xc1\x94B\xf8\xa2#\x82\x98a\xf9\xffY\x12\xe3v\x18L\xff\x14Fl\xeb\x0ff\x10\xc4\xb0\xa2\xb9y\xcd-\xba%\xcd\xa5\x8ajT\xd1\x92\xa9\x0c\x86x\xb6a\xe6h\xf8\x02<g\xaa\xaf\xf6\xdd%\x89\xae\x13z\xfe \xc6\x0b\xfb1^4p\x99\x1e6\xc6\xd4\xebK\xdbx\xf9\xc4\x8f[Iw\xf8\x89\xef\xcbQf\xcfh\xe3\x95\x8c\xebj&\xb9\xe2.\x8f\x0c\\ui\x89\xf1x\xf4\xd6\xc0kf\xc1\xf1v\xad(\xc4\xeb\x89~\xfa\xf0\x06\xa8\xa4\x7f\x93\xf4\xd7\x0c\xbcE#\xad\x92\xfc\xed\xeao\xefX\\\x03'
+        sage: loads(old_pickle)
+        [    0     a]
+        [a + 1     1]
     """
     from sage.matrix.matrix_space import MatrixSpace
 
diff --git a/src/sage/matrix/matrix_space.py b/src/sage/matrix/matrix_space.py
index e629fc0a213..58569480464 100644
--- a/src/sage/matrix/matrix_space.py
+++ b/src/sage/matrix/matrix_space.py
@@ -1781,3 +1781,5 @@ def test_trivial_matrices_inverse(ring, sparse=True, checkrank=True):
     'Matrix_integer_2x2', Matrix_integer_dense)
 register_unpickle_override('sage.matrix.matrix_integer_2x2',
     'MatrixSpace_ZZ_2x2_class', MatrixSpace)
+register_unpickle_override('sage.matrix.matrix_mod2e_dense',
+    'unpickle_matrix_mod2e_dense_v0', matrix_gf2e_dense.unpickle_matrix_gf2e_dense_v0)