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gh-115347: avoid emitting redundant NOP for the docstring with -OO #115494

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merged 2 commits into from
Feb 15, 2024
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gh-115347: avoid emitting redundant NOP for the docstring with -OO #115494

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766fba9
gh-115347: avoid emitting redundant NOP for the docstring with -OO
iritkatriel Feb 14, 2024
eaeb96f
add class with docstring to test, to cover the compiler_body case
iritkatriel Feb 15, 2024
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26 changes: 26 additions & 0 deletions Lib/test/test_compile.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
import contextlib
import dis
import io
import math
import os
import unittest
Expand Down Expand Up @@ -812,6 +814,30 @@ def unused_code_at_end():
'RETURN_CONST',
list(dis.get_instructions(unused_code_at_end))[-1].opname)

@support.cpython_only
def test_docstring_omitted(self):
# See gh-115347
src = textwrap.dedent("""
def f():
"docstring1"
def h():
"docstring2"
return 42

class C:
"docstring3"
pass

return h
""")
for opt in [-1, 0, 1, 2]:
with self.subTest(opt=opt):
code = compile(src, "<test>", "exec", optimize=opt)
output = io.StringIO()
with contextlib.redirect_stdout(output):
dis.dis(code)
self.assertNotIn('NOP' , output.getvalue())

def test_dont_merge_constants(self):
# Issue #25843: compile() must not merge constants which are equal
# but have a different type.
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-02-14-23-50-43.gh-issue-115347.VkHvQC.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix bug where docstring was replaced by a redundant NOP when Python is run
with ``-OO``.
38 changes: 20 additions & 18 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1692,16 +1692,13 @@ compiler_unwind_fblock_stack(struct compiler *c, location *ploc,
static int
compiler_body(struct compiler *c, location loc, asdl_stmt_seq *stmts)
{
int i = 0;
stmt_ty st;
PyObject *docstring;

/* Set current line number to the line number of first statement.
This way line number for SETUP_ANNOTATIONS will always
coincide with the line number of first "real" statement in module.
If body is empty, then lineno will be set later in optimize_and_assemble. */
if (c->u->u_scope_type == COMPILER_SCOPE_MODULE && asdl_seq_LEN(stmts)) {
st = (stmt_ty)asdl_seq_GET(stmts, 0);
stmt_ty st = (stmt_ty)asdl_seq_GET(stmts, 0);
loc = LOC(st);
}
/* Every annotated class and module should have __annotations__. */
Expand All @@ -1711,24 +1708,25 @@ compiler_body(struct compiler *c, location loc, asdl_stmt_seq *stmts)
if (!asdl_seq_LEN(stmts)) {
return SUCCESS;
}
/* if not -OO mode, set docstring */
if (c->c_optimize < 2) {
docstring = _PyAST_GetDocString(stmts);
if (docstring) {
Py_ssize_t first_instr = 0;
PyObject *docstring = _PyAST_GetDocString(stmts);
if (docstring) {
first_instr = 1;
/* if not -OO mode, set docstring */
if (c->c_optimize < 2) {
PyObject *cleandoc = _PyCompile_CleanDoc(docstring);
if (cleandoc == NULL) {
return ERROR;
}
i = 1;
st = (stmt_ty)asdl_seq_GET(stmts, 0);
stmt_ty st = (stmt_ty)asdl_seq_GET(stmts, 0);
assert(st->kind == Expr_kind);
location loc = LOC(st->v.Expr.value);
ADDOP_LOAD_CONST(c, loc, cleandoc);
Py_DECREF(cleandoc);
RETURN_IF_ERROR(compiler_nameop(c, NO_LOCATION, &_Py_ID(__doc__), Store));
}
}
for (; i < asdl_seq_LEN(stmts); i++) {
for (Py_ssize_t i = first_instr; i < asdl_seq_LEN(stmts); i++) {
VISIT(c, stmt, (stmt_ty)asdl_seq_GET(stmts, i));
}
return SUCCESS;
Expand Down Expand Up @@ -2239,7 +2237,6 @@ static int
compiler_function_body(struct compiler *c, stmt_ty s, int is_async, Py_ssize_t funcflags,
int firstlineno)
{
PyObject *docstring = NULL;
arguments_ty args;
identifier name;
asdl_stmt_seq *body;
Expand All @@ -2266,28 +2263,33 @@ compiler_function_body(struct compiler *c, stmt_ty s, int is_async, Py_ssize_t f
RETURN_IF_ERROR(
compiler_enter_scope(c, name, scope_type, (void *)s, firstlineno));

/* if not -OO mode, add docstring */
if (c->c_optimize < 2) {
docstring = _PyAST_GetDocString(body);
if (docstring) {
Py_ssize_t first_instr = 0;
PyObject *docstring = _PyAST_GetDocString(body);
if (docstring) {
first_instr = 1;
/* if not -OO mode, add docstring */
if (c->c_optimize < 2) {
docstring = _PyCompile_CleanDoc(docstring);
if (docstring == NULL) {
compiler_exit_scope(c);
return ERROR;
}
}
else {
docstring = NULL;
}
}
if (compiler_add_const(c->c_const_cache, c->u, docstring ? docstring : Py_None) < 0) {
Py_XDECREF(docstring);
compiler_exit_scope(c);
return ERROR;
}
Py_XDECREF(docstring);
Py_CLEAR(docstring);

c->u->u_metadata.u_argcount = asdl_seq_LEN(args->args);
c->u->u_metadata.u_posonlyargcount = asdl_seq_LEN(args->posonlyargs);
c->u->u_metadata.u_kwonlyargcount = asdl_seq_LEN(args->kwonlyargs);
for (Py_ssize_t i = docstring ? 1 : 0; i < asdl_seq_LEN(body); i++) {
for (Py_ssize_t i = first_instr; i < asdl_seq_LEN(body); i++) {
VISIT_IN_SCOPE(c, stmt, (stmt_ty)asdl_seq_GET(body, i));
}
if (c->u->u_ste->ste_coroutine || c->u->u_ste->ste_generator) {
Expand Down