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GH-94979: Pop the exception stack when jumping out of exception handlers. #95003

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merged 2 commits into from
Jul 19, 2022
Merged

GH-94979: Pop the exception stack when jumping out of exception handlers. #95003

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bb9f9c8
Pop the exception stack when jumping out of exception handlers.
markshannon Jul 19, 2022
9b0111c
Assert that popped value is an exception or None.
markshannon Jul 19, 2022
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61 changes: 52 additions & 9 deletions Objects/frameobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -182,10 +182,31 @@ pop_value(int64_t stack)
return Py_ARITHMETIC_RIGHT_SHIFT(int64_t, stack, BITS_PER_BLOCK);
}

#define MASK ((1<<BITS_PER_BLOCK)-1)

static inline Kind
top_of_stack(int64_t stack)
{
return stack & ((1<<BITS_PER_BLOCK)-1);
return stack & MASK;
}

static inline Kind
peek(int64_t stack, int n)
{
assert(n >= 1);
return (stack>>(BITS_PER_BLOCK*(n-1))) & MASK;
}

static Kind
stack_swap(int64_t stack, int n)
{
assert(n >= 1);
Kind to_swap = peek(stack, n);
Kind top = top_of_stack(stack);
int shift = BITS_PER_BLOCK*(n-1);
int64_t replaced_low = (stack & ~(MASK << shift)) | (top << shift);
int64_t replaced_top = (replaced_low & ~MASK) | to_swap;
return replaced_top;
}

static int64_t
Expand Down Expand Up @@ -218,6 +239,7 @@ tos_char(int64_t stack) {
case Null:
return 'N';
}
return '?';
}

static void
Expand Down Expand Up @@ -371,6 +393,7 @@ mark_stacks(PyCodeObject *code_obj, int len)
stacks[i+1] = next_stack;
break;
case POP_EXCEPT:
assert(top_of_stack(next_stack) == Except);
next_stack = pop_value(next_stack);
stacks[i+1] = next_stack;
break;
Expand Down Expand Up @@ -420,6 +443,20 @@ mark_stacks(PyCodeObject *code_obj, int len)
stacks[i+1] = next_stack;
break;
}
case SWAP:
{
int n = get_arg(code, i);
next_stack = stack_swap(next_stack, n);
stacks[i+1] = next_stack;
break;
}
case COPY:
{
int n = get_arg(code, i);
next_stack = push_value(next_stack, peek(next_stack, n));
stacks[i+1] = next_stack;
break;
}
default:
{
int delta = PyCompile_OpcodeStackEffect(opcode, _Py_OPARG(code[i]));
Expand Down Expand Up @@ -556,13 +593,6 @@ first_line_not_before(int *lines, int len, int line)
return result;
}

static void
frame_stack_pop(PyFrameObject *f)
{
PyObject *v = _PyFrame_StackPop(f->f_frame);
Py_XDECREF(v);
}

static PyFrameState
_PyFrame_GetState(PyFrameObject *frame)
{
Expand Down Expand Up @@ -782,7 +812,20 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
start_stack = pop_value(start_stack);
}
while (start_stack > best_stack) {
frame_stack_pop(f);
if (top_of_stack(start_stack) == Except) {
/* Pop exception stack as well as the evaluation stack */
PyThreadState *tstate = _PyThreadState_GET();
_PyErr_StackItem *exc_info = tstate->exc_info;
PyObject *value = exc_info->exc_value;
PyObject *exc = _PyFrame_StackPop(f->f_frame);
assert(PyExceptionInstance_Check(exc) || exc == Py_None);
exc_info->exc_value = exc;
Py_XDECREF(value);
}
else {
PyObject *v = _PyFrame_StackPop(f->f_frame);
Py_XDECREF(v);
}
start_stack = pop_value(start_stack);
}
/* Finally set the new lasti and return OK. */
Expand Down