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Re: Pointer to invalid multibyte sequence in mbsnrtowcs()
- From: Igor Liferenko <igor dot liferenko at gmail dot com>
- To: "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>
- Cc: libc-help <libc-help at sourceware dot org>
- Date: Tue, 20 Dec 2016 08:34:40 +0700
- Subject: Re: Pointer to invalid multibyte sequence in mbsnrtowcs()
- Authentication-results: sourceware.org; auth=none
Hi Michael,
It seems that *src is not changed to point to invalid multibyte
sequence only when dest is NULL.
There are two possible cases:
1) incomplete multibyte character is at the end of input buffer *)
2) incomplete multibyte character is not at the end of input buffer *)
*) - end of buffer is determined by nms argument.
The examples 1.1 and 2.1 demonstrate that when dest is NULL, *src is
not changed.
The examples 1.2 and 2.2 demenstrate that *src is correctly changed
when dest is not NULL.
It is unclear whether it is POSIX behavior (and thus mbsnrtowcs(3)
should be corrected), or it is a bug.
Example 1.1 (at the end of buffer, dest is NULL):
#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
setlocale(LC_CTYPE, "en_US.UTF-8");
char *s = "\321\216\321";
const char *x = s;
printf("status: %d\n", mbsnrtowcs(NULL,&x,strlen(s),0,NULL));
perror(NULL);
printf("ori=%p\nnew=%p\n",(void *)s,(void *)x);
return 0;
}
Output 1.1:
status: 1
Success
ori=0x56337c86d910
new=0x56337c86d910
Example 2.1 (not at the end of buffer, dest is NULL):
#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
setlocale(LC_CTYPE, "en_US.UTF-8");
char *s = "\321\216\321\321\215";
const char *x = s;
printf("status: %d\n", mbsnrtowcs(NULL,&x,strlen(s),0,NULL));
perror(NULL);
printf("ori=%p\nnew=%p\n",(void *)s,(void *)x);
return 0;
}
Output 2.1:
status: -1
Invalid or incomplete multibyte or wide character
ori=0x55ad82792910
new=0x55ad82792910
Example 1.2 (at the end of buffer, dest is not NULL):
#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
setlocale(LC_CTYPE, "en_US.UTF-8");
char *s = "\321\216\321";
const char *x = s;
wchar_t *wcs = calloc(strlen(s) + 1, sizeof(wchar_t));
printf("status: %d\n", mbsnrtowcs(wcs,&x,strlen(s),strlen(s),NULL));
perror(NULL);
printf("ori=%p\nnew=%p\n",(void *)s,(void *)x);
return 0;
}
Output 1.2:
status: 1
Success
ori=0x556497c29980
new=0x556497c29983
Example 2.2 (not at the end of buffer, dest is not NULL):
#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
setlocale(LC_CTYPE, "en_US.UTF-8");
char *s = "\321\216\321\321\215";
const char *x = s;
wchar_t *wcs = calloc(strlen(s) + 1, sizeof(wchar_t));
printf("status: %d\n", mbsnrtowcs(wcs,&x,strlen(s),strlen(s),NULL));
perror(NULL);
printf("ori=%p\nnew=%p\n",(void *)s,(void *)x);
return 0;
}
Output 2.2:
status: -1
Invalid or incomplete multibyte or wide character
ori=0x55bb1aa98980
new=0x55bb1aa98982
Thanks,
Igor