Consolidate gdb.GdbError handling

I noticed two nearly identical copies of the same code for handling
gdb.GdbError.  The only differences were in some error messages.
These differences didn't seem very important, so this patch pulls the
code out into a new function.

2018-09-23  Tom Tromey  <tom@tromey.com>

	* python/py-function.c (fnpy_call): Use gdbpy_handle_exception.
	* python/py-cmd.c (cmdpy_function): Use gdbpy_handle_exception.
	* python/python-internal.h (gdbpy_handle_exception): Declare.
	* python/py-utils.c (gdbpy_handle_exception): New function.

1 files changed, 56 insertions, 0 deletions

diff --git a/gdb/python/py-utils.c b/gdb/python/py-utils.c
index 01fd6ad..6ef0d7e 100644
--- a/gdb/python/py-utils.c
+++ b/gdb/python/py-utils.c
@@ -384,3 +384,59 @@ gdb_pymodule_addobject (PyObject *module, const char *name, PyObject *object)
     Py_DECREF (object);
   return result;
 }
+
+/* Handle a Python exception when the special gdb.GdbError treatment
+   is desired.  This should only be called when an exception is set.
+   If the exception is a gdb.GdbError, throw a gdb exception with the
+   exception text.  For other exceptions, print the Python stack and
+   then throw a gdb exception.  */
+
+void
+gdbpy_handle_exception ()
+{
+  PyObject *ptype, *pvalue, *ptraceback;
+
+  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.  */
+
+  gdb::unique_xmalloc_ptr<char>
+    msg (gdbpy_exception_to_string (ptype, pvalue));
+
+  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 Python "
+			 "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: %s"), msg.get ());
+      else
+	error (_("Error occurred in Python."));
+    }
+  else
+    {
+      Py_XDECREF (ptype);
+      Py_XDECREF (pvalue);
+      Py_XDECREF (ptraceback);
+      error ("%s", msg.get ());
+    }
+}