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gvanrossumgvanrossum
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Add warning for assignment to None, True and False. This is patch
549213 by Jeremy (checking in for him since he's away and busy).
1 parent a4deda0 commit 9c8a086

2 files changed

Lines changed: 100 additions & 30 deletions

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‎Misc/NEWS‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -84,6 +84,10 @@ Type/class unification and new-style classes
8484
Core and builtins
8585
-----------------
8686

87+
- Assignment to None has long been frowned upon. Now there's a
88+
warning message when you do this. It also warns against assignment
89+
to True or False.
90+
8791
- A frame object's f_lineno attribute can now be written to from a
8892
trace function to change which line will execute next. A command to
8993
exploit this from pdb has been added. [SF patch #643835]

‎Python/compile.c‎

Lines changed: 96 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -575,6 +575,7 @@ block_pop(struct compiling *c, int type)
575575
/* Prototype forward declarations */
576576

577577
static int issue_warning(const char *, const char *, int);
578+
static int symtable_warn(struct symtable *, char *);
578579
static int com_init(struct compiling *, const char *);
579580
static void com_free(struct compiling *);
580581
static void com_push(struct compiling *, int);
@@ -1006,6 +1007,64 @@ none_assignment_check(struct compiling *c, char *name, int assigning)
10061007
return 0;
10071008
}
10081009

1010+
static int num_literals = 3;
1011+
static char *literal_names[] = {"None", "True", "False"};
1012+
static PyObject *literals;
1013+
1014+
static int
1015+
init_literals(void)
1016+
{
1017+
int i;
1018+
1019+
literals = PyDict_New();
1020+
if (literals == NULL)
1021+
return -1;
1022+
for (i = 0; i < num_literals; i++)
1023+
if (PyDict_SetItemString(literals, literal_names[i],
1024+
Py_None) < 0)
1025+
return -1;
1026+
return 0;
1027+
}
1028+
1029+
static int
1030+
check_literal(PyObject *name, struct compiling *c, struct symtable *st)
1031+
{
1032+
/* check for literal names that will become keywords in the future */
1033+
if (literals == NULL && init_literals() < 0)
1034+
return -1;
1035+
if (!PyString_Check(name))
1036+
return -1;
1037+
if (PyDict_GetItem(literals, name)) {
1038+
char buf[1024];
1039+
PyOS_snprintf(buf, sizeof(buf), "'%s' may become a keyword",
1040+
PyString_AS_STRING(name));
1041+
if (c && (issue_warning(buf, c->c_filename, c->c_lineno) < 0))
1042+
return -1;
1043+
if (st && (symtable_warn(st, buf) < 0))
1044+
return -1;
1045+
}
1046+
return 0;
1047+
}
1048+
1049+
static int
1050+
check_literal_str(const char *name, struct compiling *c, struct symtable *st)
1051+
{
1052+
int i;
1053+
1054+
for (i = 0; i < num_literals; i++)
1055+
if (strcmp(literal_names[i], name) == 0) {
1056+
char buf[1024];
1057+
PyOS_snprintf(buf, sizeof(buf),
1058+
"'%s' may become a keyword", name);
1059+
if (c &&
1060+
issue_warning(buf, c->c_filename, c->c_lineno) < 0)
1061+
return -1;
1062+
if (st && symtable_warn(st, buf) < 0)
1063+
return -1;
1064+
}
1065+
return 0;
1066+
}
1067+
10091068
static void
10101069
com_addop_varname(struct compiling *c, int kind, char *name)
10111070
{
@@ -1063,6 +1122,14 @@ com_addop_varname(struct compiling *c, int kind, char *name)
10631122
}
10641123
Py_DECREF(v);
10651124

1125+
if (kind == VAR_STORE || kind == VAR_DELETE) {
1126+
if (check_literal(v, c, NULL) < 0) {
1127+
c->c_errors++;
1128+
i = 255;
1129+
goto done;
1130+
}
1131+
}
1132+
10661133
switch (kind) {
10671134
case VAR_LOAD:
10681135
switch (scope) {
@@ -1130,6 +1197,7 @@ com_addopname(struct compiling *c, int op, node *n)
11301197
/* XXX it is possible to write this code without the 1000
11311198
chars on the total length of dotted names, I just can't be
11321199
bothered right now */
1200+
11331201
if (TYPE(n) == STAR)
11341202
name = "*";
11351203
else if (TYPE(n) == dotted_name) {
@@ -1138,6 +1206,10 @@ com_addopname(struct compiling *c, int op, node *n)
11381206
name = buffer;
11391207
for (i = 0; i < NCH(n); i += 2) {
11401208
char *s = STR(CHILD(n, i));
1209+
if (check_literal_str(s, c, NULL) < 0) {
1210+
name = NULL;
1211+
break;
1212+
}
11411213
if (p + strlen(s) > buffer + (sizeof buffer) - 2) {
11421214
com_error(c, PyExc_MemoryError,
11431215
"dotted_name too long");
@@ -1153,6 +1225,8 @@ com_addopname(struct compiling *c, int op, node *n)
11531225
else {
11541226
REQ(n, NAME);
11551227
name = STR(n);
1228+
if (check_literal_str(name, c, NULL) < 0)
1229+
name = NULL;
11561230
}
11571231
com_addop_name(c, op, name);
11581232
}
@@ -2972,9 +3046,13 @@ com_import_stmt(struct compiling *c, node *n)
29723046
} else {
29733047
tup = PyTuple_New((NCH(n) - 2)/2);
29743048
for (i = 3; i < NCH(n); i += 2) {
3049+
char *s = STR(CHILD(CHILD(n, i), 0));
3050+
if (check_literal_str(s, c, NULL) < 0) {
3051+
c->c_errors++;
3052+
return;
3053+
}
29753054
PyTuple_SET_ITEM(tup, (i-3)/2,
2976-
PyString_FromString(STR(
2977-
CHILD(CHILD(n, i), 0))));
3055+
PyString_FromString(s));
29783056
}
29793057
}
29803058
com_addoparg(c, LOAD_CONST, com_addconst(c, tup));
@@ -3914,40 +3992,23 @@ com_fplist(struct compiling *c, node *n)
39143992
static void
39153993
com_arglist(struct compiling *c, node *n)
39163994
{
3917-
int nch, i, narg;
3995+
int i;
39183996
int complex = 0;
3919-
char nbuf[30];
39203997
REQ(n, varargslist);
39213998
/* varargslist:
39223999
(fpdef ['=' test] ',')* (fpdef ['=' test] | '*' .....) */
3923-
nch = NCH(n);
3924-
/* Enter all arguments in table of locals */
3925-
for (i = 0, narg = 0; i < nch; i++) {
3926-
node *ch = CHILD(n, i);
3927-
node *fp;
3928-
if (TYPE(ch) == STAR || TYPE(ch) == DOUBLESTAR)
3929-
break;
3930-
REQ(ch, fpdef); /* fpdef: NAME | '(' fplist ')' */
3931-
fp = CHILD(ch, 0);
3932-
if (TYPE(fp) != NAME) {
3933-
PyOS_snprintf(nbuf, sizeof(nbuf), ".%d", i);
4000+
/* Check if the argument list includes nested tuples */
4001+
for (i = 0; i < NCH(n); i++)
4002+
if (TYPE(CHILD(n, i)) == LPAR) {
39344003
complex = 1;
3935-
}
3936-
narg++;
3937-
/* all name updates handled by symtable */
3938-
if (++i >= nch)
39394004
break;
3940-
ch = CHILD(n, i);
3941-
if (TYPE(ch) == EQUAL)
3942-
i += 2;
3943-
else
3944-
REQ(ch, COMMA);
3945-
}
4005+
}
4006+
/* If it does, generate code to unpack them. */
39464007
if (complex) {
39474008
/* Generate code for complex arguments only after
39484009
having counted the simple arguments */
39494010
int ilocal = 0;
3950-
for (i = 0; i < nch; i++) {
4011+
for (i = 0; i < NCH(n); i++) {
39514012
node *ch = CHILD(n, i);
39524013
node *fp;
39534014
if (TYPE(ch) == STAR || TYPE(ch) == DOUBLESTAR)
@@ -3960,7 +4021,7 @@ com_arglist(struct compiling *c, node *n)
39604021
com_fpdef(c, ch);
39614022
}
39624023
ilocal++;
3963-
if (++i >= nch)
4024+
if (++i >= NCH(n))
39644025
break;
39654026
ch = CHILD(n, i);
39664027
if (TYPE(ch) == EQUAL)
@@ -5359,7 +5420,7 @@ static void
53595420
symtable_params(struct symtable *st, node *n)
53605421
{
53615422
int i, complex = -1, ext = 0;
5362-
node *c = NULL;
5423+
node *c = NULL, *ch = NULL;
53635424

53645425
if (TYPE(n) == parameters) {
53655426
n = CHILD(n, 1);
@@ -5376,9 +5437,14 @@ symtable_params(struct symtable *st, node *n)
53765437
if (TYPE(c) == test) {
53775438
continue;
53785439
}
5379-
if (TYPE(CHILD(c, 0)) == NAME)
5440+
ch = CHILD(c, 0);
5441+
if (TYPE(ch) == NAME) {
5442+
if (check_literal_str(STR(ch), NULL, st) < 0) {
5443+
st->st_errors++;
5444+
return;
5445+
}
53805446
symtable_add_def(st, STR(CHILD(c, 0)), DEF_PARAM);
5381-
else {
5447+
} else {
53825448
char nbuf[30];
53835449
PyOS_snprintf(nbuf, sizeof(nbuf), ".%d", i);
53845450
symtable_add_def(st, nbuf, DEF_PARAM);

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