#3021: Antoine Pitrou's Lexical exception handlers

2 files changed, 15 insertions, 7 deletions

diff --git a/Include/frameobject.h b/Include/frameobject.h
index d2afe8b..65ebd2a 100644
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -27,13 +27,13 @@ typedef struct _frame {
     PyObject **f_stacktop;
     PyObject *f_trace;		/* Trace function */
 
-    /* If an exception is raised in this frame, the next three are used to
-     * record the exception info (if any) originally in the thread state.  See
-     * comments before set_exc_info() -- it's not obvious.
-     * Invariant:  if _type is NULL, then so are _value and _traceback.
-     * Desired invariant:  all three are NULL, or all three are non-NULL.  That
-     * one isn't currently true, but "should be".
-     */
+	/* In a generator, we need to be able to swap between the exception
+	   state inside the generator and the exception state of the calling
+	   frame (which shouldn't be impacted when the generator "yields"
+	   from an except handler).
+	   These three fields exist exactly for that, and are unused for
+	   non-generator frames. See the SAVE_EXC_STATE and SWAP_EXC_STATE
+	   macros in ceval.c for details of their use. */
     PyObject *f_exc_type, *f_exc_value, *f_exc_traceback;
 
     PyThreadState *f_tstate;
diff --git a/Include/opcode.h b/Include/opcode.h
index 7bdf1c9..6da9877 100644
--- a/Include/opcode.h
+++ b/Include/opcode.h
@@ -70,6 +70,7 @@ extern "C" {
 #define YIELD_VALUE	86
 #define POP_BLOCK	87
 #define END_FINALLY	88
+#define POP_EXCEPT	89
 
 #define HAVE_ARGUMENT	90	/* Opcodes from here have an argument: */
 
@@ -133,6 +134,13 @@ extern "C" {
 #define EXTENDED_ARG  143
 
 
+/* EXCEPT_HANDLER is a special, implicit block type which is created when
+   entering an except handler. It is not an opcode but we define it here
+   as we want it to be available to both frameobject.c and ceval.c, while
+   remaining private.*/
+#define EXCEPT_HANDLER 257
+
+
 enum cmp_op {PyCmp_LT=Py_LT, PyCmp_LE=Py_LE, PyCmp_EQ=Py_EQ, PyCmp_NE=Py_NE, PyCmp_GT=Py_GT, PyCmp_GE=Py_GE,
 	     PyCmp_IN, PyCmp_NOT_IN, PyCmp_IS, PyCmp_IS_NOT, PyCmp_EXC_MATCH, PyCmp_BAD};