test-perror: relax test to ignore cygwin bug glibc was not the only platform where fprintf(fopen(,"r")) fails to detect errors; cygwin 1.7.9 is another culprit (although it will be fixed for 1.7.10), and I suspect that several other platforms were failing perror2 for the same reason. At this point, there are so many functions affected, and the way to avoid the bug is easy enough (don't pass bogus streams to output-producing functions), that I'm not worried about fixing things other than to document them. * tests/test-perror2.c (main): Relax test on requiring detection of stream errors, and use unbuffered stream. * doc/posix-functions/dprintf.texi (dprintf): Document bug. * doc/posix-functions/fprintf.texi (fprintf): Likewise. * doc/posix-functions/fputc.texi (fputc): Likewise. * doc/posix-functions/fputs.texi (fputs): Likewise. * doc/posix-functions/fputws.texi (fputws): Likewise. * doc/posix-functions/fwprintf.texi (fwprintf): Likewise. * doc/posix-functions/fwrite.texi (fwrite): Likewise. * doc/posix-functions/getopt.texi (getopt): Likewise. * doc/posix-functions/perror.texi (perror): Likewise. * doc/posix-functions/printf.texi (printf): Likewise. * doc/posix-functions/psiginfo.texi (psiginfo): Likewise. * doc/posix-functions/psignal.texi (psignal): Likewise. * doc/posix-functions/putc.texi (putc): Likewise. * doc/posix-functions/putc_unlocked.texi (putc_unlocked): Likewise. * doc/posix-functions/putchar.texi (putchar): Likewise. * doc/posix-functions/putchar_unlocked.texi (putchar_unlocked): Likewise. * doc/posix-functions/puts.texi (puts): Likewise. * doc/posix-functions/putwc.texi (putwc): Likewise. * doc/posix-functions/putwchar.texi (putwchar): Likewise. * doc/posix-functions/vdprintf.texi (vdprintf): Likewise. * doc/posix-functions/vfprintf.texi (vfprintf): Likewise. * doc/posix-functions/vfwprintf.texi (vfwprintf): Likewise. * doc/posix-functions/vprintf.texi (vprintf): Likewise. * doc/posix-functions/vwprintf.texi (vwprintf): Likewise. * doc/posix-functions/wordexp.texi (wordexp): Likewise. * doc/posix-functions/wprintf.texi (wprintf): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>

--- a/doc/posix-functions/putwc.texi
+++ b/doc/posix-functions/putwc.texi
@@ -18,4 +18,8 @@
 @item
 On AIX and Windows platforms, @code{wchar_t} is a 16-bit type and therefore cannot
 accommodate all Unicode characters.
+@item
+On some platforms, this function does not set @code{errno} or the
+stream error indicator on attempts to write to a read-only stream:
+Cygwin 1.7.9.
 @end itemize