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py/compile: Fix bug with break/continue in else of optimised for-range. 

This patch fixes a bug whereby the Python stack was not correctly reset if
there was a break/continue statement in the else black of an optimised
for-range loop.

For example, in the following code the "j" variable from the inner for loop
was not being popped off the Python stack:

    for i in range(4):
        for j in range(4):
            pass
        else:
            continue

This is now fixed with this patch.
This commit is contained in:
Damien George 2017-06-22 13:50:33 +10:00
parent 458cbacb8f
commit 4c5f108321
1 changed files with 19 additions and 2 deletions
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21
py/compile.c
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@ -1406,7 +1406,20 @@ STATIC void compile_for_stmt_optimised_range(compiler_t *comp, mp_parse_node_t p
// break/continue apply to outer loop (if any) in the else block
END_BREAK_CONTINUE_BLOCK
compile_node(comp, pn_else);
// Compile the else block. We must pop the iterator variables before
// executing the else code because it may contain break/continue statements.
uint end_label = 0;
if (!MP_PARSE_NODE_IS_NULL(pn_else)) {
// discard final value of "var", and possible "end" value
EMIT(pop_top);
if (end_on_stack) {
EMIT(pop_top);
}
compile_node(comp, pn_else);
end_label = comp_next_label(comp);
EMIT_ARG(jump, end_label);
EMIT_ARG(adjust_stack_size, 1 + end_on_stack);
}
EMIT_ARG(label_assign, break_label);
@ -1417,6 +1430,10 @@ STATIC void compile_for_stmt_optimised_range(compiler_t *comp, mp_parse_node_t p
if (end_on_stack) {
EMIT(pop_top);
}
if (!MP_PARSE_NODE_IS_NULL(pn_else)) {
EMIT_ARG(label_assign, end_label);
}
}
STATIC void compile_for_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
@ -1496,7 +1513,7 @@ STATIC void compile_for_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
// break/continue apply to outer loop (if any) in the else block
END_BREAK_CONTINUE_BLOCK
compile_node(comp, pns->nodes[3]); // else (not tested)
compile_node(comp, pns->nodes[3]); // else (may be empty)
EMIT_ARG(label_assign, break_label);
}