[RFA v2 2/2] Fix PR python/17386 - add __index__ method to gdb.Value

[Tom Tromey <tom@tromey.com>]

This patch fixes PR python/17386.

The bug is that gdb.Value does not implement the Python __index__
method.  This method is needed to convert a Python object to an index
and is used by various operations in Python, such as indexing an
array.

The fix is to implement the nb_index method for gdb.Value.

nb_index was added in Python 2.5.  I don't have a good way to test
Python 2.4, but I made an attempt to accomodate it.

I chose to use valpy_long in all cases because this simplifies porting
to Python 3, and because there didn't seem to be any harm.

Built and regtested on x86-64 Fedora 23.

2016-05-23  Tom Tromey  <tom@tromey.com>

	PR python/17386:
	* python/py-value.c (value_object_as_number): Add
	nb_inplace_floor_divide, nb_inplace_true_divide, nb_index.

2016-05-23  Tom Tromey  <tom@tromey.com>

	PR python/17386:
	* gdb.python/py-value.exp (test_value_numeric_ops): Add tests that
	use value as an index.
---
 gdb/ChangeLog                         | 6 ++++++
 gdb/python/py-value.c                 | 8 +++++++-
 gdb/testsuite/ChangeLog               | 6 ++++++
 gdb/testsuite/gdb.python/py-value.exp | 7 +++++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5142429..a848c14 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2016-05-23  Tom Tromey  <tom@tromey.com>
 
+	PR python/17386:
+	* python/py-value.c (value_object_as_number): Add
+	nb_inplace_floor_divide, nb_inplace_true_divide, nb_index.
+
+2016-05-23  Tom Tromey  <tom@tromey.com>
+
 	* python/py-value.c (value_object_as_number): Add
 	nb_inplace_divide for Python 2.
 
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 268f6c8..e0b017a 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -1838,7 +1838,13 @@ static PyNumberMethods value_object_as_number = {
   NULL,                       /* nb_inplace_xor */
   NULL,                       /* nb_inplace_or */
   NULL,                       /* nb_floor_divide */
-  valpy_divide                /* nb_true_divide */
+  valpy_divide,               /* nb_true_divide */
+  NULL,			      /* nb_inplace_floor_divide */
+  NULL			      /* nb_inplace_true_divide */
+#ifndef HAVE_LIBPYTHON_2_4
+  /* This was added in Python 2.5.  */
+  , valpy_long		      /* nb_index */
+#endif /* HAVE_LIBPYTHON_2_4 */
 };
 
 static PyMappingMethods value_object_as_mapping = {
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 1f0e3f9..edcf3b2 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,11 @@
 2016-05-23  Tom Tromey  <tom@tromey.com>
 
+	PR python/17386:
+	* gdb.python/py-value.exp (test_value_numeric_ops): Add tests that
+	use value as an index.
+
+2016-05-23  Tom Tromey  <tom@tromey.com>
+
 	PR python/19438, PR python/18393:
 	* gdb.python/py-progspace.exp: Add "dir" test.
 	* gdb.python/py-objfile.exp: Add "dir" test.
diff --git a/gdb/testsuite/gdb.python/py-value.exp b/gdb/testsuite/gdb.python/py-value.exp
index a9dbe97..57a9ba1 100644
--- a/gdb/testsuite/gdb.python/py-value.exp
+++ b/gdb/testsuite/gdb.python/py-value.exp
@@ -124,6 +124,13 @@ proc test_value_numeric_ops {} {
   gdb_test "python print ('result = ' + str(b-2))" " = 0x3( <.*>)?" "subtract python integer from pointer value"
   gdb_test "python print ('result = ' + str(b-a))" " = 3" "subtract two pointer values"
 
+  gdb_test "python print ('result = ' + 'result'\[gdb.Value(0)\])" \
+    "result = r" "use value as string index"
+  gdb_test "python print ('result = ' + str((1,2,3)\[gdb.Value(0)\]))" \
+    "result = 1" "use value as tuple index"
+  gdb_test "python print ('result = ' + str(\[1,2,3\]\[gdb.Value(0)\]))" \
+    "result = 1" "use value as array index"
+
   # Test some invalid operations.
 
   gdb_test_multiple "python print ('result = ' + str(i+'foo'))" "catch error in python type conversion" {
-- 
2.5.5