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Date: Mon, 4 Jan 2010 12:29:13 +0000
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Subject: Re: Cygwin 1.7.1 sprintf() with format string having 8th bit set
From: Andy Koppe <andy DOT koppe AT gmail DOT com>
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2010/1/4 Joseph Quinsey
> In Cygwin 1,7.1, sprintf() with the format string having an 8th bit set
> appears to be broken. Sample code (where I've indicated the backslashes in
> the comments, in case they are stripped out by the mailer):
>
> #include <stdio.h>
>
> int main (void)
> {
> =C2=A0 =C2=A0unsigned char foo[30] =3D "";
> =C2=A0 =C2=A0unsigned char bar[30] =3D "";
> =C2=A0 =C2=A0unsigned char xxx[30] =3D "";
> =C2=A0 =C2=A0sprintf (foo, "\100%s", "ABCD"); /* this is backslash one ze=
ro zero =C2=A0 */
> =C2=A0 =C2=A0sprintf (bar, "\300%s", "ABCD"); /* this is backslash three =
zero zero */
> =C2=A0 =C2=A0sprintf (xxx, "\300ABCD"); =C2=A0 =C2=A0 =C2=A0 /* this is b=
ackslash three zero zero */
> =C2=A0 =C2=A0printf ("%d %d %d %d %d\n", foo[0],foo[1],foo[2],foo[3],foo[=
4]);
> =C2=A0 =C2=A0printf ("%d %d %d %d %d\n", bar[0],bar[1],bar[2],bar[3],bar[=
4]);
> =C2=A0 =C2=A0printf ("%d %d %d %d %d\n", xxx[0],xxx[1],xxx[2],xxx[3],xxx[=
4]);
> =C2=A0 =C2=A0return 0;
> }
>
> gives:
>
> 64 65 66 67 68
> 0 0 0 0 0
> 192 65 66 67 68
>
> The second line of the output should be the same as the third.

The issue here is that the character set of the "C" locale in Cygwin
1.7 is UTF-8 and that the \300 on its own is an invalid UTF-8 byte. To
get well-defined behaviour, you need to invoke setlocale(LC_CTYPE,
...) with the approriate locale.

See the thread at http://cygwin.com/ml/cygwin/2009-12/msg00980.html
for more on this.

Andy

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