io: replace local_isatty() with a proper function __isatty_nostatus()

Replace local_isatty() inlined in libio with a proper function
__isatty_nostatus(). This allows simpler system-specific
implementations that don't need to touch errno at all.

Note: I left the prototype in include/unistd.h (the internal header
file.) It didn't much make sense to me to put it in a different header
(not-cancel.h), but perhaps someone can elucidate the need.

Add such an implementation for Linux, with a generic fallback.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/include/unistd.h b/include/unistd.h
index e241603b8131a9e9dc8571a1857443bdd20e206a..376ab5a93688c39544251c68cf19c9f6a6734a03 100644 (file)
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -152,6 +152,7 @@ libc_hidden_proto (__ttyname_r)
 extern __pid_t _Fork (void);
 libc_hidden_proto (_Fork);
 extern int __isatty (int __fd) attribute_hidden;
+extern int __isatty_nostatus (int __fd) attribute_hidden;
 extern int __link (const char *__from, const char *__to);
 extern int __symlink (const char *__from, const char *__to);
 extern int __symlinkat (const char *__from, int __fd, const char *__to);

diff --git a/io/Makefile b/io/Makefile
index e06f3cb3dba1b35003d9ea9117ccaa69e957f55b..edee38e233d866965cb214e3e2d149a229b3cae2 100644 (file)
--- a/io/Makefile
+++ b/io/Makefile
@@ -92,6 +92,7 @@ routines := \
   getdirname \
   getwd \
   isatty \
+  isatty_nostatus \
   lchmod \
   lchown \
   link \

diff --git a/io/isatty_nostatus.c b/io/isatty_nostatus.c
new file mode 100644 (file)
index 0000000..e8ee796
--- /dev/null
+++ b/io/isatty_nostatus.c
@@ -0,0 +1,29 @@
+/* Copyright (C) 1991-2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <unistd.h>
+
+/* Return 1 if FD is a terminal, 0 if not, without changing errno  */
+int
+__isatty_nostatus (int fd)
+{
+  int save_errno = errno;
+  int res = __isatty (fd);
+  __set_errno (save_errno);
+  return res;
+}

diff --git a/libio/filedoalloc.c b/libio/filedoalloc.c
index 9ddd75b42923100f7d4115c128fb9b315226f903..f360d96a9b573450d715cd7cd9793ff48f4584c0 100644 (file)
--- a/libio/filedoalloc.c
+++ b/libio/filedoalloc.c
@@ -61,16 +61,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-/* Return the result of isatty, without changing errno.  */
-static int
-local_isatty (int fd)
-{
-  int save_errno = errno;
-  int res = __isatty (fd);
-  __set_errno (save_errno);
-  return res;
-}
-
 /* Allocate a file buffer, or switch to unbuffered I/O.  Streams for
    TTY devices default to line buffered.  */
 int
@@ -90,7 +80,7 @@ _IO_file_doallocate (FILE *fp)
 #ifdef DEV_TTY_P
              DEV_TTY_P (&st) ||
 #endif
-             local_isatty (fp->_fileno))
+             __isatty_nostatus (fp->_fileno))
            fp->_flags |= _IO_LINE_BUF;
        }
 #if defined _STATBUF_ST_BLKSIZE

diff --git a/sysdeps/unix/sysv/linux/isatty_nostatus.c b/sysdeps/unix/sysv/linux/isatty_nostatus.c
new file mode 100644 (file)
index 0000000..7f110be
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/isatty_nostatus.c
@@ -0,0 +1,29 @@
+/* Copyright (C) 1991-2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <termios.h>
+#include <kernel_termios.h>
+#include <sys/ioctl.h>
+
+/* Return 1 if FD is a terminal, 0 if not, without changing errno  */
+int
+__isatty_nostatus (int fd)
+{
+  struct __kernel_termios k_termios;
+  return INTERNAL_SYSCALL_CALL (ioctl, fd, TCGETS, &k_termios) == 0;
+}