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Date: Thu, 13 Sep 2018 09:27:55 -0700
From: Benjamin Peterson <benjamin@...hon.org>
To: musl@...ts.openwall.com
Subject: [PATCH] improve error handling of ttyname_r and isatty

POSIX allows ttyname(_r) and isatty to return EBADF if passed file descriptor is
invalid.
---
 src/unistd/isatty.c    | 6 +++++-
 src/unistd/ttyname_r.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/unistd/isatty.c b/src/unistd/isatty.c
index c8badaf5..3d5213c6 100644
--- a/src/unistd/isatty.c
+++ b/src/unistd/isatty.c
@@ -1,9 +1,13 @@
 #include <unistd.h>
+#include <errno.h>
 #include <sys/ioctl.h>
 #include "syscall.h"
 
 int isatty(int fd)
 {
 	struct winsize wsz;
-	return !__syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz);
+	unsigned long r = __syscall_ret(__syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz));
+	if (r == 0) return 1;
+	if (errno != EBADF) errno = ENOTTY;
+	return 0;
 }
diff --git a/src/unistd/ttyname_r.c b/src/unistd/ttyname_r.c
index 33aa4ae1..3f836a6a 100644
--- a/src/unistd/ttyname_r.c
+++ b/src/unistd/ttyname_r.c
@@ -10,7 +10,10 @@ int ttyname_r(int fd, char *name, size_t size)
 	char procname[sizeof "/proc/self/fd/" + 3*sizeof(int) + 2];
 	ssize_t l;
 
-	if (!isatty(fd)) return ENOTTY;
+	if (!isatty(fd)) {
+		if (errno != EBADF) errno = ENOTTY;
+		return errno;
+	}
 
 	__procfdname(procname, fd);
 	l = readlink(procname, name, size);
-- 
2.17.1

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