Re: [patch] Allow gdb.Values to become callable if appropriate.

[Phil Muldoon <pmuldoon@redhat.com>]

On 20/07/10 23:17, Tom Tromey wrote:
>>>>>> "Phil" == Phil Muldoon <pmuldoon@redhat.com> writes:

> Phil> Comments?
> 
> Looks good.
> 
> Phil> +A @code{gdb.Value} that represents a function or a function pointer is a
> Phil> +callable Python object.
> 
> From what I can see, your patch explicitly excludes function pointers.
> 
> This may be a bit too strict.  I think it would be reasonably safe and
> easy to accept references (via coerce_ref) and also function pointers
> (doing a single dereference inside the new function).
> 
> Alternatively, update the documentation.

I thought a little about this.  I'd rather be more strict here, and
update the documentation purely because of the side-effects of
inferior calls.  What do you think?

Patch attached.

Cheers,

Phil

--

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index be6cd3d..813fe41 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -20608,6 +20608,22 @@ bar = some_val['foo']
 
 Again, @code{bar} will also be a @code{gdb.Value} object.
 
+A @code{gdb.Value} that represents a function can be executed via
+inferior function call.  Any arguments provided to the call must match
+the function prototype of the function, and must be provided in the
+same order expected in that prototype.
+
+For example, @code{some_val} is a @code{gdb.Value} instance
+representing a function that takes two integers as arguments.  To
+execute this function, call it like so:
+
+@smallexample
+result = some_val (10,20)
+@end smallexample
+
+Any values returned from a function call will be stored as a
+@code{gdb.Value}.
+
 The following attributes are provided:
 
 @table @code
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 2024021..d547ed1 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -25,6 +25,7 @@
 #include "language.h"
 #include "dfp.h"
 #include "valprint.h"
+#include "infcall.h"
 
 #ifdef HAVE_PYTHON
 
@@ -393,6 +394,53 @@ valpy_setitem (PyObject *self, PyObject *key, PyObject *value)
   return -1;
 }
 
+/* Called by the Python interpreter to perform an inferior function
+   call on the value.  */
+static PyObject *
+valpy_call (PyObject *self, PyObject *args, PyObject *keywords)
+{
+  struct value *return_value = NULL;
+  Py_ssize_t args_count;
+  volatile struct gdb_exception except;
+  struct value *function = ((value_object *) self)->value;
+  struct value **vargs = NULL;
+  struct type *ftype = check_typedef (value_type (function));
+
+  if (TYPE_CODE (ftype) != TYPE_CODE_FUNC)
+    {
+      PyErr_SetString (PyExc_RuntimeError,
+		       _("Value is not callable (not TYPE_CODE_FUNC)."));
+      return NULL;
+    }
+
+  args_count = PyTuple_Size (args);
+  if (args_count > 0)
+    {
+      int i;
+
+      vargs = alloca (sizeof (struct value *) * args_count);
+      for (i = 0; i < args_count; i++)
+	{
+	  PyObject *item = PyTuple_GetItem (args, i);
+
+	  if (item == NULL)
+	    return NULL;
+
+	  vargs[i] = convert_value_from_python (item);
+	  if (vargs[i] == NULL)
+	    return NULL;
+	}
+    }
+
+  TRY_CATCH (except, RETURN_MASK_ALL)
+    {
+      return_value = call_function_by_hand (function, args_count, vargs);
+    }
+  GDB_PY_HANDLE_EXCEPTION (except);
+
+  return value_to_value_object (return_value);
+}
+
 /* Called by the Python interpreter to obtain string representation
    of the object.  */
 static PyObject *
@@ -1151,7 +1199,7 @@ PyTypeObject value_object_type = {
   0,				  /*tp_as_sequence*/
   &value_object_as_mapping,	  /*tp_as_mapping*/
   valpy_hash,		          /*tp_hash*/
-  0,				  /*tp_call*/
+  valpy_call,	                  /*tp_call*/
   valpy_str,			  /*tp_str*/
   0,				  /*tp_getattro*/
   0,				  /*tp_setattro*/
diff --git a/gdb/testsuite/gdb.python/py-value.c b/gdb/testsuite/gdb.python/py-value.c
index be933b3..7481bd5 100644
--- a/gdb/testsuite/gdb.python/py-value.c
+++ b/gdb/testsuite/gdb.python/py-value.c
@@ -15,6 +15,8 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include <stdio.h>
+
 struct s
 {
   int a;
@@ -44,6 +46,16 @@ void ptr_ref(int*& rptr_int)
 }
 #endif
 
+void func1 ()
+{
+  printf ("void function called\n");
+}
+
+int func2 (int arg1, int arg2)
+{
+  return arg1 + arg2;
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -53,6 +65,8 @@ main (int argc, char *argv[])
   PTR x = &s;
   char st[17] = "divide et impera";
   char nullst[17] = "divide\0et\0impera";
+  void (*fp1) (void)  = &func1;
+  int  (*fp2) (int, int) = &func2;
   const char *sptr = "pointer";
   const char *embed = "embedded x\201\202\203\204";
   int a[3] = {1,2,3};
@@ -63,6 +77,8 @@ main (int argc, char *argv[])
   s.a = 3;
   s.b = 5;
   u.a = 7;
+  (*fp1) ();
+  (*fp2) (10,20);
 
 #ifdef __cplusplus
   ptr_ref(ptr_i);
diff --git a/gdb/testsuite/gdb.python/py-value.exp b/gdb/testsuite/gdb.python/py-value.exp
index a24bc11..eaed9c7 100644
--- a/gdb/testsuite/gdb.python/py-value.exp
+++ b/gdb/testsuite/gdb.python/py-value.exp
@@ -276,6 +276,35 @@ proc test_lazy_strings {} {
 }
 
 
+proc test_inferior_function_call {} {
+    global gdb_prompt hex decimal
+
+    # Correct inferior call without arguments.
+    gdb_test "p/x fp1" " = $hex.*"
+    gdb_py_test_silent_cmd "python fp1 = gdb.history (0)" "get value from history" 1
+    gdb_test "python fp1 = fp1.dereference()" ""
+    gdb_test "python result = fp1()" ""
+    gdb_test "python print result" "void"
+
+    # Correct inferior call with arguments.
+    gdb_test "p/x fp2" " = $hex.*"
+    gdb_py_test_silent_cmd "python fp2 = gdb.history (0)" "get value from history" 1
+    gdb_test "python fp2 = fp2.dereference()" ""
+    gdb_test "python result2 = fp2(10,20)" ""
+    gdb_test "python print result2" "30"
+
+    # Incorrect to call an int value.
+    gdb_test "p i" " = $decimal.*"
+    gdb_py_test_silent_cmd "python i = gdb.history (0)" "get value from history" 1
+    gdb_test "python result3 = i()" ".*Value is not callable.*"
+
+    # Incorrect number of arguments.
+    gdb_test "p/x fp2" " = $hex.*"
+    gdb_py_test_silent_cmd "python fp3 = gdb.history (0)" "get value from history" 1
+    gdb_test "python fp3 = fp3.dereference()" ""
+    gdb_test "python result2 = fp3(10)" ".*Too few arguments in function call.*"
+}
+
 # A few objfile tests.
 proc test_objfiles {} {
     gdb_test "python\nok=False\nfor file in gdb.objfiles():\n  if 'py-value' in file.filename:\n    ok=True\nprint ok\nend" "True"
@@ -435,6 +464,7 @@ if ![runto_main] then {
 }
 
 test_value_in_inferior
+test_inferior_function_call
 test_lazy_strings
 test_value_after_death