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perror() changes the orientation of stderr to byte-oriented mode if stderr is not oriented yet.




POSIX states:
The perror() function shall not change the orientation of the standard
error stream.

However, cygwin perror() function changes the orientation of stderr to
byte-oriented mode if stderr is not oriented yet.

Simple test case (chkperror.c) attached checks this behavior.

Expected result:
0
äöü: Invalid argument
0
äöü
1
äöü: Invalid argument

However, cygwin result:
0
äöü: Invalid argument
-1
▒▒▒
-1
äöü: Invalid argument

I have made a patch to solve this problem, attached. However, I am not
sure that calling _write_r() here is correct manner. I will appreciate
if anyone familiar with libc code comment or make suggestions.

-- 
Takashi Yano <takashi.yano@xxxxxxxxxxx>

Attachment: 0001-Fix-a-bug-of-perror-which-changes-the-orientation-of.patch
Description: Binary data

#include <stdio.h>
#include <wchar.h>
#include <locale.h>
#include <errno.h>

int main()
{
	setlocale(LC_CTYPE, "de_DE.UTF-8");
	errno = EINVAL;
	printf("%d\n", fwide(stderr, 0));
	perror("äöü");
	printf("%d\n", fwide(stderr, 0));
	fwprintf(stderr, L"äöü\n");
	printf("%d\n", fwide(stderr, 0));
	perror("äöü");
	return 0;
}

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