From 511d70738bce11a67219d0132ce725c323d00e4e Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sun, 5 May 2019 22:50:57 -0400
Subject: [PATCH] make fgetwc set error indicator for stream on encoding errors

this is a requirement in POSIX that's omitted, and seemed potentially
non-conforming, in the C standard. as such it was omitted here.
however, as part of Austin Group issue #1170, the discrepancy was
raised with WG14 and determined to be unintended; future versions of
the C standard will require the error indicator to be set, as POSIX
does.
---
 src/stdio/fgetwc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/stdio/fgetwc.c b/src/stdio/fgetwc.c
index 0801e28f..aa10b818 100644
--- a/src/stdio/fgetwc.c
+++ b/src/stdio/fgetwc.c
@@ -25,12 +25,18 @@ static wint_t __fgetwc_unlocked_internal(FILE *f)
 	do {
 		b = c = getc_unlocked(f);
 		if (c < 0) {
-			if (!first) errno = EILSEQ;
+			if (!first) {
+				f->flags |= F_ERR;
+				errno = EILSEQ;
+			}
 			return WEOF;
 		}
 		l = mbrtowc(&wc, (void *)&b, 1, &st);
 		if (l == -1) {
-			if (!first) ungetc(b, f);
+			if (!first) {
+				f->flags |= F_ERR;
+				ungetc(b, f);
+			}
 			return WEOF;
 		}
 		first = 0;