[PATCH] Implement floordiv operator for gdb.Value

[Jonathan Wakely <jwakely@redhat.com>]

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This is my attempt to implement the // operator on gdb.Value objects.
There is already BINOP_INTDIV which works fine for integral types, but
for floats I use BINOP_DIV and then call floor() on the result. This
doesn't support decimal floats though.

Is this a reasonable solution? Is the test sufficient?

I have a follow-up patch which changes the meaning of the / operator
for gdb.Value when built against Python 3, to be consistent with
Python (see comment 1 in the Bugzilla PR) but I expect that to be more
controversial :-)


gdb/ChangeLog:
2016-09-20  Jonathan Wakely  <jwakely@redhat.com>

	PR python/20624
	* python/py-value.c (VALPY_FLOORDIV): Define new enumerator.
	(valpy_binop_throw): Handle VALPY_FLOORDIV.
	(valpy_floordiv): New function.
	(value_object_as_number): Set valpy_floordiv in relevant slot.

gdb/testsuite/ChangeLog:
2016-09-20  Jonathan Wakely  <jwakely@redhat.com>

	PR python/20624
	* gdb.python/py-value.exp: Test floor division.

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commit 3a019f3ba61bde5320419f5782d8f2554ac55ace
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Sep 20 10:38:35 2016 +0100

    gdb: Implement floordiv operator for gdb.Value
    
    gdb/ChangeLog:
    2016-09-20  Jonathan Wakely  <jwakely@redhat.com>
    
    	PR python/20624
    	* python/py-value.c (VALPY_FLOORDIV): Define new enumerator.
    	(valpy_binop_throw): Handle VALPY_FLOORDIV.
    	(valpy_floordiv): New function.
    	(value_object_as_number): Set valpy_floordiv in relevant slot.
    
    gdb/testsuite/ChangeLog:
    2016-09-20  Jonathan Wakely  <jwakely@redhat.com>
    
    	PR python/20624
    	* gdb.python/py-value.exp: Test floor division.

diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 21e9247..f6a6c11 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -1011,7 +1011,8 @@ enum valpy_opcode
   VALPY_RSH,
   VALPY_BITAND,
   VALPY_BITOR,
-  VALPY_BITXOR
+  VALPY_BITXOR,
+  VALPY_FLOORDIV
 };
 
 /* If TYPE is a reference, return the target; otherwise return TYPE.  */
@@ -1032,6 +1033,7 @@ valpy_binop_throw (enum valpy_opcode opcode, PyObject *self, PyObject *other)
   struct value *res_val = NULL;
   enum exp_opcode op = OP_NULL;
   int handled = 0;
+  bool floor_it = false;
 
   /* If the gdb.Value object is the second operand, then it will be
      passed to us as the OTHER argument, and SELF will be an entirely
@@ -1113,6 +1115,22 @@ valpy_binop_throw (enum valpy_opcode opcode, PyObject *self, PyObject *other)
     case VALPY_REM:
       op = BINOP_REM;
       break;
+    case VALPY_FLOORDIV:
+      {
+        struct type *ltype = value_type (arg1);
+        struct type *rtype = value_type (arg2);
+        ltype = check_typedef (ltype);
+        rtype = check_typedef (rtype);
+        if (TYPE_CODE (ltype) == TYPE_CODE_FLT
+            || TYPE_CODE (rtype) == TYPE_CODE_FLT)
+          {
+            op = BINOP_DIV;
+            floor_it = true;
+          }
+        else
+          op = BINOP_INTDIV;
+      }
+      break;
     case VALPY_POW:
       op = BINOP_EXP;
       break;
@@ -1142,7 +1160,15 @@ valpy_binop_throw (enum valpy_opcode opcode, PyObject *self, PyObject *other)
     }
 
   if (res_val)
-    result = value_to_value_object (res_val);
+    {
+      if (floor_it)
+        {
+          double d = value_as_double (res_val);
+          d = floor (d);
+          res_val = value_from_double (value_type (res_val), d);
+        }
+      result = value_to_value_object (res_val);
+    }
 
   do_cleanups (cleanup);
   return result;
@@ -1200,6 +1226,12 @@ valpy_remainder (PyObject *self, PyObject *other)
 }
 
 static PyObject *
+valpy_floordiv (PyObject *self, PyObject *other)
+{
+  return valpy_binop (VALPY_FLOORDIV, self, other);
+}
+
+static PyObject *
 valpy_power (PyObject *self, PyObject *other, PyObject *unused)
 {
   /* We don't support the ternary form of pow.  I don't know how to express
@@ -1837,7 +1869,7 @@ static PyNumberMethods value_object_as_number = {
   NULL,                       /* nb_inplace_and */
   NULL,                       /* nb_inplace_xor */
   NULL,                       /* nb_inplace_or */
-  NULL,                       /* nb_floor_divide */
+  valpy_floordiv,             /* nb_floor_divide */
   valpy_divide,               /* nb_true_divide */
   NULL,			      /* nb_inplace_floor_divide */
   NULL,			      /* nb_inplace_true_divide */
diff --git a/gdb/testsuite/gdb.python/py-value.exp b/gdb/testsuite/gdb.python/py-value.exp
index 57a9ba1..81837e9 100644
--- a/gdb/testsuite/gdb.python/py-value.exp
+++ b/gdb/testsuite/gdb.python/py-value.exp
@@ -87,6 +87,8 @@ proc test_value_numeric_ops {} {
   gdb_test "python print ('result = ' + str(f/g))" " = 0.5" "divide two double values"
   gdb_test "python print ('result = ' + str(i%j))" " = 1" "take remainder of two integer values"
   # Remainder of float is implemented in Python but not in GDB's value system.
+  gdb_test "python print ('result = ' + str(i//j))" " = 2" "floor-divide two integer values"
+  gdb_test "python print ('result = ' + str(f//g))" " = 0" "floor-divide two double values"
 
   gdb_test "python print ('result = ' + str(i**j))" " = 25" "integer value raised to the power of another integer value"
   gdb_test "python print ('result = ' + str(g**j))" " = 6.25" "double value raised to the power of integer value"