[python] [patch] Fix PR/12183

[Phil Muldoon <pmuldoon at redhat dot com>]

This patch fixes PR python/12183.  In this case GDB was printing a stack
trace for a gdb.GdbError.  This is incorrect, GdbErrors should not
produce a stack trace.  This fix is largely a duplicate of the code
already in py-cmd.

OK?

Cheers,

Phil

2011-03-21  Phil Muldoon  <pmuldoon@redhat.com>

        PR python/12183

	* python/py-function.c (fnpy_call): Treat GdbErrors differently to
	other error classes.  Do not print stack trace.

2011-03-21  Phil Muldoon  <pmuldoon@redhat.com>

        PR python/12183

	* gdb.python/py-function.exp: Add GdbError tests.

--

diff --git a/gdb/python/py-function.c b/gdb/python/py-function.c
index 47d916b..7ba2838 100644
--- a/gdb/python/py-function.c
+++ b/gdb/python/py-function.c
@@ -77,10 +77,57 @@ fnpy_call (struct gdbarch *gdbarch, const struct language_defn *language,
   Py_DECREF (callable);
   Py_DECREF (args);
 
-  if (!result)
+  if (! result)
     {
-      gdbpy_print_stack ();
-      error (_("Error while executing Python code."));
+      PyObject *ptype, *pvalue, *ptraceback;
+      char *msg;
+
+      PyErr_Fetch (&ptype, &pvalue, &ptraceback);
+
+      /* Try to fetch an error message contained within ptype, pvalue.
+	 When fetching the error message we need to make our own copy,
+	 we no longer own ptype, pvalue after the call to PyErr_Restore.  */
+
+      msg = gdbpy_exception_to_string (ptype, pvalue);
+      make_cleanup (xfree, msg);
+
+      if (msg == NULL)
+	{
+	  /* An error occurred computing the string representation of the
+	     error message.  This is rare, but we should inform the user.  */
+
+	  printf_filtered (_("An error occurred in a Python "
+			     "convenience function\n"
+			     "and then another occurred computing the "
+			     "error message.\n"));
+	  gdbpy_print_stack ();
+	}
+
+      /* Don't print the stack for gdb.GdbError exceptions.
+	 It is generally used to flag user errors.
+
+	 We also don't want to print "Error occurred in Python command"
+	 for user errors.  However, a missing message for gdb.GdbError
+	 exceptions is arguably a bug, so we flag it as such.  */
+
+      if (! PyErr_GivenExceptionMatches (ptype, gdbpy_gdberror_exc)
+	  || msg == NULL || *msg == '\0')
+	{
+	  PyErr_Restore (ptype, pvalue, ptraceback);
+	  gdbpy_print_stack ();
+	  if (msg != NULL && *msg != '\0')
+	    error (_("Error occurred in Python convenience function: %s"),
+		   msg);
+	  else
+	    error (_("Error occurred in Python convenience function."));
+	}
+      else
+	{
+	  Py_XDECREF (ptype);
+	  Py_XDECREF (pvalue);
+	  Py_XDECREF (ptraceback);
+	  error ("%s", msg);
+	}
     }
 
   value = convert_value_from_python (result);
diff --git a/gdb/testsuite/gdb.python/py-function.exp b/gdb/testsuite/gdb.python/py-function.exp
index bbbbf42..dfccdff 100644
--- a/gdb/testsuite/gdb.python/py-function.exp
+++ b/gdb/testsuite/gdb.python/py-function.exp
@@ -69,3 +69,29 @@ gdb_py_test_multiple "input int-returning function" \
 
 gdb_test "print \$yes() && \$yes()" " = 1" "call yes with &&"
 gdb_test "print \$yes() || \$yes()" " = 1" "call yes with ||"
+
+gdb_py_test_multiple "Test GDBError" \
+  "python" "" \
+  "class GDBError(gdb.Function):" "" \
+  "    def __init__(self):" "" \
+  "        gdb.Function.__init__(self, 'gdberror')" "" \
+  "    def invoke(self):" "" \
+  "        raise gdb.GdbError(\"This is a GdbError\")" "" \
+  "GDBError ()" "" \
+  "end" ""
+
+gdb_test "print \$gdberror()" "This is a GdbError.*" \
+    "Test GdbError.  There should not be a stack trace"
+
+gdb_py_test_multiple "Test Normal Error" \
+  "python" "" \
+  "class NormalError(gdb.Function):" "" \
+  "    def __init__(self):" "" \
+  "        gdb.Function.__init__(self, 'normalerror')" "" \
+  "    def invoke(self):" "" \
+  "        raise RuntimeError(\"This is a Normal Error\")" "" \
+  "NormalError ()" "" \
+  "end" ""
+
+gdb_test "print \$normalerror()" "Traceback.*File.*line 5.*in invoke.*RuntimeError.*This is a Normal Error.*" \
+    "Test a Runtime error.  There should be a stack trace."