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Fix larger than WCHAR_MAX differences in wcs{,n}cmp (#795)

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The C standard states:

> Unless explicitly stated otherwise, the functions described in this
> subclause order two wide characters the same way as two integers of
> the underlying integer type designated by wchar_t.
>
> [...]
>
> The wcscmp function returns an integer greater than, equal to, or
> less than zero, accordingly as the wide string pointed to by s1 is
> greater than, equal to, or less than the wide string pointed to by
> s2.
>
> [...]
>
> The wcsncmp function returns an integer greater than, equal to, or
> less than zero, accordingly as the possibly null-terminated array
> pointed to by s1 is greater than, equal to, or less than the
> possibly null-terminated array pointed to by s2.
- C Standard, 7.31.4.4. Wide string comparison functions

Cosmopolitan fails to obey this in cases where the difference between
two wide characters is larger than WCHAR_MAX.

This means that, for example, the following program:

 #include <stdio.h>
 #include <wchar.h>
 #include <limits.h>

int main()
{
    wchar_t str1[] = { WCHAR_MIN, L'\0' };
    wchar_t str2[] = { WCHAR_MAX, L'\0' };
    printf("%d\n", wcscmp(str1, str2));
    printf("%d\n", wcsncmp(str1, str2, 2));
}

will print `1` twice, instead of the negative numbers mandated by the
standard (as WCHAR_MIN is less than WCHAR_MAX)

This patch fixes this, along with the associated Github issue,
https://github.com/jart/cosmopolitan/issues/783
This commit is contained in:
Gabriel Ravier 2023-03-30 02:28:18 +02:00 • committed by GitHub
parent 999481ace0
commit ba42248575
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
3 changed files with 10 additions and 10 deletions
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2
libc/str/wcscmp.c
View file

@ -30,5 +30,5 @@ int wcscmp(const wchar_t *a, const wchar_t *b) {
size_t i = 0;
if (a == b) return 0;
while (a[i] == b[i] && b[i]) ++i;
return (unsigned)a[i] - (unsigned)b[i];
return (a[i] > b[i]) - (a[i] < b[i]);
}

2
libc/str/wcsncmp.c
View file

@ -30,5 +30,5 @@ int wcsncmp(const wchar_t *a, const wchar_t *b, size_t n) {
size_t i = 0;
if (!n-- || a == b) return 0;
while (i < n && a[i] == b[i] && b[i]) ++i;
return (unsigned)a[i] - (unsigned)b[i];
return (a[i] > b[i]) - (a[i] < b[i]);
}

16
test/libc/str/strcmp_test.c
View file

@ -460,11 +460,11 @@ TEST(wcscmp, testTwosComplementBane) {
EXPECT_EQ(wcscmp(memcpy(B1, "\x00\x00\x00\x80", 4),
memcpy(B2, "\x00\x00\x00\x80", 4)),
0);
EXPECT_EQ(-1, wcscmp(memcpy(B1, "\xff\xff\xff\x7f", 4),
memcpy(B2, "\x00\x00\x00\x80", 4)));
EXPECT_EQ(wcscmp(memcpy(B1, "\x00\x00\x00\x80", 4),
EXPECT_LT(0, wcscmp(memcpy(B1, "\xff\xff\xff\x7f", 4),
memcpy(B2, "\x00\x00\x00\x80", 4)));
EXPECT_LT(wcscmp(memcpy(B1, "\x00\x00\x00\x80", 4),
memcpy(B2, "\xff\xff\xff\x7f", 4)),
1);
0);
free(B2);
free(B1);
}
@ -475,12 +475,12 @@ TEST(wcsncmp, testTwosComplementBane) {
EXPECT_EQ(wcsncmp(memcpy(B1, "\x00\x00\x00\x80", 4),
memcpy(B2, "\x00\x00\x00\x80", 4), 1),
0);
EXPECT_EQ(wcsncmp(memcpy(B1, "\xff\xff\xff\x7f", 4),
EXPECT_GT(wcsncmp(memcpy(B1, "\xff\xff\xff\x7f", 4),
memcpy(B2, "\x00\x00\x00\x80", 4), 1),
-1);
EXPECT_EQ(wcsncmp(memcpy(B1, "\x00\x00\x00\x80", 4),
0);
EXPECT_LT(wcsncmp(memcpy(B1, "\x00\x00\x00\x80", 4),
memcpy(B2, "\xff\xff\xff\x7f", 4), 1),
1);
0);
free(B2);
free(B1);
}