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bpo-37830: Fix compilation of break and continue in finally. #15320

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Aug 24, 2019
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bpo-37830: Fix compilation of break and continue in finally. #15320

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ebcf476
bpo-37830: Fix compilation of break and continue in finally.
serhiy-storchaka Aug 17, 2019
0d5be4c
Test conditional "break" and "continue". Add tests for the "while" lo…
serhiy-storchaka Aug 17, 2019
686bd90
Optimize bytecode for common case.
serhiy-storchaka Aug 18, 2019
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Optimize bytecode for common case.
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@serhiy-storchaka
serhiy-storchaka committed Aug 18, 2019
commit 686bd900a5595137494250f21c6219852b58e57e
84 changes: 41 additions & 43 deletions Lib/test/test_dis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -977,51 +977,49 @@ def jumpy():
Instruction(opname='LOAD_CONST', opcode=100, arg=6, argval='Who let lolcatz into this test suite?', argrepr="'Who let lolcatz into this test suite?'", offset=96, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=98, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=100, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=0, argval=None, argrepr='None', offset=102, starts_line=20, is_jump_target=True),
Instruction(opname='SETUP_FINALLY', opcode=122, arg=70, argval=176, argrepr='to 176', offset=104, starts_line=None, is_jump_target=False),
Instruction(opname='SETUP_FINALLY', opcode=122, arg=12, argval=120, argrepr='to 120', offset=106, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=5, argval=1, argrepr='1', offset=108, starts_line=21, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=7, argval=0, argrepr='0', offset=110, starts_line=None, is_jump_target=False),
Instruction(opname='BINARY_TRUE_DIVIDE', opcode=27, arg=None, argval=None, argrepr='', offset=112, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=114, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=116, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=28, argval=148, argrepr='to 148', offset=118, starts_line=None, is_jump_target=False),
Instruction(opname='DUP_TOP', opcode=4, arg=None, argval=None, argrepr='', offset=120, starts_line=22, is_jump_target=True),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=2, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=122, starts_line=None, is_jump_target=False),
Instruction(opname='COMPARE_OP', opcode=107, arg=10, argval='exception match', argrepr='exception match', offset=124, starts_line=None, is_jump_target=False),
Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=146, argval=146, argrepr='', offset=126, starts_line=None, is_jump_target=False),
Instruction(opname='SETUP_FINALLY', opcode=122, arg=70, argval=174, argrepr='to 174', offset=102, starts_line=20, is_jump_target=True),
Instruction(opname='SETUP_FINALLY', opcode=122, arg=12, argval=118, argrepr='to 118', offset=104, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=5, argval=1, argrepr='1', offset=106, starts_line=21, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=8, argval=0, argrepr='0', offset=108, starts_line=None, is_jump_target=False),
Instruction(opname='BINARY_TRUE_DIVIDE', opcode=27, arg=None, argval=None, argrepr='', offset=110, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=112, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=114, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=28, argval=146, argrepr='to 146', offset=116, starts_line=None, is_jump_target=False),
Instruction(opname='DUP_TOP', opcode=4, arg=None, argval=None, argrepr='', offset=118, starts_line=22, is_jump_target=True),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=2, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=120, starts_line=None, is_jump_target=False),
Instruction(opname='COMPARE_OP', opcode=107, arg=10, argval='exception match', argrepr='exception match', offset=122, starts_line=None, is_jump_target=False),
Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=144, argval=144, argrepr='', offset=124, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=126, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=128, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=130, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=132, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=134, starts_line=23, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=8, argval='Here we go, here we go, here we go...', argrepr="'Here we go, here we go, here we go...'", offset=136, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=138, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=140, starts_line=None, is_jump_target=False),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=142, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=26, argval=172, argrepr='to 172', offset=144, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=146, starts_line=None, is_jump_target=True),
Instruction(opname='LOAD_FAST', opcode=124, arg=0, argval='i', argrepr='i', offset=148, starts_line=25, is_jump_target=True),
Instruction(opname='SETUP_WITH', opcode=143, arg=14, argval=166, argrepr='to 166', offset=150, starts_line=None, is_jump_target=False),
Instruction(opname='STORE_FAST', opcode=125, arg=1, argval='dodgy', argrepr='dodgy', offset=152, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=154, starts_line=26, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=9, argval='Never reach this', argrepr="'Never reach this'", offset=156, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=158, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=160, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=162, starts_line=None, is_jump_target=False),
Instruction(opname='BEGIN_FINALLY', opcode=53, arg=None, argval=None, argrepr='', offset=164, starts_line=None, is_jump_target=False),
Instruction(opname='WITH_CLEANUP_START', opcode=81, arg=None, argval=None, argrepr='', offset=166, starts_line=None, is_jump_target=True),
Instruction(opname='WITH_CLEANUP_FINISH', opcode=82, arg=None, argval=None, argrepr='', offset=168, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=170, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=172, starts_line=None, is_jump_target=True),
Instruction(opname='BEGIN_FINALLY', opcode=53, arg=None, argval=None, argrepr='', offset=174, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=176, starts_line=28, is_jump_target=True),
Instruction(opname='LOAD_CONST', opcode=100, arg=10, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=178, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=180, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=182, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=184, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=186, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=0, argval=None, argrepr='None', offset=188, starts_line=None, is_jump_target=False),
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=190, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=132, starts_line=23, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=9, argval='Here we go, here we go, here we go...', argrepr="'Here we go, here we go, here we go...'", offset=134, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=136, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=138, starts_line=None, is_jump_target=False),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=140, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=26, argval=170, argrepr='to 170', offset=142, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=144, starts_line=None, is_jump_target=True),
Instruction(opname='LOAD_FAST', opcode=124, arg=0, argval='i', argrepr='i', offset=146, starts_line=25, is_jump_target=True),
Instruction(opname='SETUP_WITH', opcode=143, arg=14, argval=164, argrepr='to 164', offset=148, starts_line=None, is_jump_target=False),
Instruction(opname='STORE_FAST', opcode=125, arg=1, argval='dodgy', argrepr='dodgy', offset=150, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=152, starts_line=26, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=10, argval='Never reach this', argrepr="'Never reach this'", offset=154, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=156, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=158, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=160, starts_line=None, is_jump_target=False),
Instruction(opname='BEGIN_FINALLY', opcode=53, arg=None, argval=None, argrepr='', offset=162, starts_line=None, is_jump_target=False),
Instruction(opname='WITH_CLEANUP_START', opcode=81, arg=None, argval=None, argrepr='', offset=164, starts_line=None, is_jump_target=True),
Instruction(opname='WITH_CLEANUP_FINISH', opcode=82, arg=None, argval=None, argrepr='', offset=166, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=168, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=170, starts_line=None, is_jump_target=True),
Instruction(opname='BEGIN_FINALLY', opcode=53, arg=None, argval=None, argrepr='', offset=172, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=174, starts_line=28, is_jump_target=True),
Instruction(opname='LOAD_CONST', opcode=100, arg=7, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=176, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=178, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=180, starts_line=None, is_jump_target=False),
Instruction(opname='END_FINALLY', opcode=88, arg=None, argval=None, argrepr='', offset=182, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=0, argval=None, argrepr='None', offset=184, starts_line=None, is_jump_target=False),
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=186, starts_line=None, is_jump_target=False),
]

# One last piece of inspect fodder to check the default line number handling
Expand Down
7 changes: 3 additions & 4 deletions Objects/frameobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -233,6 +233,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
* the 'finally' blocks. */
memset(blockstack, '\0', sizeof(blockstack));
blockstack_top = 0;
unsigned char prevop = NOP;
for (addr = 0; addr < code_len; addr += sizeof(_Py_CODEUNIT)) {
unsigned char op = code[addr];
switch (op) {
Expand Down Expand Up @@ -267,10 +268,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
* we're jumping out of. */
delta++;
}
else if (op == SETUP_FINALLY &&
code[target_addr] != POP_TOP &&
code[target_addr] != DUP_TOP)
{
else if (prevop == LOAD_CONST) {
/* Pops None pushed before SETUP_FINALLY. */
delta++;
}
Expand Down Expand Up @@ -303,6 +301,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
break;
}
}
prevop = op;
}

/* Verify that the blockstack tracking code didn't get lost. */
Expand Down
62 changes: 43 additions & 19 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,7 @@ It's called a frame block to distinguish it from a basic block in the
compiler IR.
*/

enum fblocktype { WHILE_LOOP, FOR_LOOP, EXCEPT, FINALLY_TRY, FINALLY_END,
enum fblocktype { WHILE_LOOP, FOR_LOOP, EXCEPT, FINALLY_TRY, FINALLY_TRY2, FINALLY_END,
WITH, ASYNC_WITH, HANDLER_CLEANUP };

struct fblockinfo {
Expand Down Expand Up @@ -1664,6 +1664,7 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
return 1;

case FINALLY_END:
info->fb_exit = NULL;
ADDOP_I(c, POP_FINALLY, preserve_tos);
if (preserve_tos) {
ADDOP(c, ROT_TWO);
Expand All @@ -1684,6 +1685,11 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
return 1;

case FINALLY_TRY:
ADDOP(c, POP_BLOCK);
ADDOP_JREL(c, CALL_FINALLY, info->fb_exit);
return 1;

case FINALLY_TRY2:
ADDOP(c, POP_BLOCK);
if (preserve_tos) {
ADDOP(c, ROT_TWO);
Expand Down Expand Up @@ -2847,23 +2853,19 @@ compiler_continue(struct compiler *c)

/* Code generated for "try: <body> finally: <finalbody>" is as follows:

LOAD_CONST None
SETUP_FINALLY L
<code for body>
POP_BLOCK
BEGIN_FINALLY
L:
<code for finalbody>
END_FINALLY
POP_TOP

The special instructions use the block stack. Each block
stack entry contains the instruction that created it (here
SETUP_FINALLY), the level of the value stack at the time the
block stack entry was created, and a label (here L).

LOAD_CONST None:
Pushes a placeholder for the value of "return".
SETUP_FINALLY:
Pushes the current value stack level and the label
onto the block stack.
Expand All @@ -2874,8 +2876,6 @@ compiler_continue(struct compiler *c)
END_FINALLY:
Pops 1 (NULL or int) or 6 entries from the *value* stack and restore
the raised and the caught exceptions they specify.
POP_TOP:
Pops a None pushed before SETUP_FINALLY.

The block stack is unwound when an exception is raised:
when a SETUP_FINALLY entry is found, the raised and the caught
Expand All @@ -2887,18 +2887,47 @@ compiler_continue(struct compiler *c)
static int
compiler_try_finally(struct compiler *c, stmt_ty s)
{
basicblock *body, *end;
basicblock *start, *newcurblock, *body, *end;
int break_finally = 1;

body = compiler_new_block(c);
end = compiler_new_block(c);
if (body == NULL || end == NULL)
return 0;

start = c->u->u_curblock;

/* `finally` block. Compile it first to determine if any of "break",
"continue" or "return" are used in it. */
compiler_use_next_block(c, end);
if (!compiler_push_fblock(c, FINALLY_END, end, end))
return 0;
VISIT_SEQ(c, stmt, s->v.Try.finalbody);
ADDOP(c, END_FINALLY);
break_finally = (c->u->u_fblock[c->u->u_nfblocks - 1].fb_exit == NULL);
if (break_finally) {
/* Pops a placeholder. See below */
ADDOP(c, POP_TOP);
}
compiler_pop_fblock(c, FINALLY_END, end);

newcurblock = c->u->u_curblock;
c->u->u_curblock = start;
start->b_next = NULL;

/* `try` block */
ADDOP_LOAD_CONST(c, Py_None);
c->u->u_lineno_set = 0;
c->u->u_lineno = s->lineno;
c->u->u_col_offset = s->col_offset;
if (break_finally) {
/* Pushes a placeholder for the value of "return" in the "try" block
to balance the stack for "break", "continue" and "return" in
the "finally" block. */
ADDOP_LOAD_CONST(c, Py_None);
}
ADDOP_JREL(c, SETUP_FINALLY, end);
compiler_use_next_block(c, body);
if (!compiler_push_fblock(c, FINALLY_TRY, body, end))
if (!compiler_push_fblock(c, break_finally ? FINALLY_TRY2 : FINALLY_TRY, body, end))
return 0;
if (s->v.Try.handlers && asdl_seq_LEN(s->v.Try.handlers)) {
if (!compiler_try_except(c, s))
Expand All @@ -2909,16 +2938,11 @@ compiler_try_finally(struct compiler *c, stmt_ty s)
}
ADDOP(c, POP_BLOCK);
ADDOP(c, BEGIN_FINALLY);
compiler_pop_fblock(c, FINALLY_TRY, body);
compiler_pop_fblock(c, break_finally ? FINALLY_TRY2 : FINALLY_TRY, body);

c->u->u_curblock->b_next = end;
c->u->u_curblock = newcurblock;

/* `finally` block */
compiler_use_next_block(c, end);
if (!compiler_push_fblock(c, FINALLY_END, end, NULL))
return 0;
VISIT_SEQ(c, stmt, s->v.Try.finalbody);
ADDOP(c, END_FINALLY);
ADDOP(c, POP_TOP);
compiler_pop_fblock(c, FINALLY_END, end);
return 1;
}

Expand Down
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