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bpo-29104: Fixed parsing backslashes in f-strings. (#490)

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This commit is contained in:
Serhiy Storchaka 2017-05-25 13:33:55 +03:00 • committed by GitHub
parent d1c3c13fed
commit 0cd7a3f196
3 changed files with 48 additions and 21 deletions
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53
Python/ast.c
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@ -4197,9 +4197,11 @@ decode_unicode_with_escapes(struct compiling *c, const node *n, const char *s,
while (s < end) {
if (*s == '\\') {
*p++ = *s++;
if (*s & 0x80) {
if (s >= end || *s & 0x80) {
strcpy(p, "u005c");
p += 5;
if (s >= end)
break;
}
}
if (*s & 0x80) { /* XXX inefficient */
@ -4352,30 +4354,37 @@ fstring_find_literal(const char **str, const char *end, int raw,
brace (which isn't part of a unicode name escape such as
"\N{EULER CONSTANT}"), or the end of the string. */
const char *literal_start = *str;
const char *literal_end;
int in_named_escape = 0;
const char *s = *str;
const char *literal_start = s;
int result = 0;
assert(*literal == NULL);
for (; *str < end; (*str)++) {
char ch = **str;
if (!in_named_escape && ch == '{' && (*str)-literal_start >= 2 &&
*(*str-2) == '\\' && *(*str-1) == 'N') {
in_named_escape = 1;
} else if (in_named_escape && ch == '}') {
in_named_escape = 0;
} else if (ch == '{' || ch == '}') {
while (s < end) {
char ch = *s++;
if (!raw && ch == '\\' && s < end) {
ch = *s++;
if (ch == 'N') {
if (s < end && *s++ == '{') {
while (s < end && *s++ != '}') {
}
continue;
}
break;
}
if (ch == '{' && warn_invalid_escape_sequence(c, n, ch) < 0) {
return -1;
}
}
if (ch == '{' || ch == '}') {
/* Check for doubled braces, but only at the top level. If
we checked at every level, then f'{0:{3}}' would fail
with the two closing braces. */
if (recurse_lvl == 0) {
if (*str+1 < end && *(*str+1) == ch) {
if (s < end && *s == ch) {
/* We're going to tell the caller that the literal ends
here, but that they should continue scanning. But also
skip over the second brace when we resume scanning. */
literal_end = *str+1;
*str += 2;
*str = s + 1;
result = 1;
goto done;
}
@ -4383,6 +4392,7 @@ fstring_find_literal(const char **str, const char *end, int raw,
/* Where a single '{' is the start of a new expression, a
single '}' is not allowed. */
if (ch == '}') {
*str = s - 1;
ast_error(c, n, "f-string: single '}' is not allowed");
return -1;
}
@ -4390,21 +4400,22 @@ fstring_find_literal(const char **str, const char *end, int raw,
/* We're either at a '{', which means we're starting another
expression; or a '}', which means we're at the end of this
f-string (for a nested format_spec). */
s--;
break;
}
}
literal_end = *str;
assert(*str <= end);
assert(*str == end || **str == '{' || **str == '}');
*str = s;
assert(s <= end);
assert(s == end || *s == '{' || *s == '}');
done:
if (literal_start != literal_end) {
if (literal_start != s) {
if (raw)
*literal = PyUnicode_DecodeUTF8Stateful(literal_start,
literal_end-literal_start,
s - literal_start,
NULL, NULL);
else
*literal = decode_unicode_with_escapes(c, n, literal_start,
literal_end-literal_start);
s - literal_start);
if (!*literal)
return -1;
}