I compiled the following program as static binaries both on Ubuntu 26.04
and Ubuntu 25.04.
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/tty.h>
int main(int argc, char *argv[]) {
struct winsize w;
int fd;
if (argc != 2) {
fprintf(stderr, "Usage: %s <device>\n", argv[0]);
return 1;
}
// Open the specified device
fd = open(argv[1], O_RDONLY);
if (fd < 0) {
perror("Failed to open device");
return 1;
}
// Use ioctl to check if the device is a TTY
printf("Check for TTY via ioctl(TIOCGWINSZ)\n");
if (ioctl(fd, TIOCGWINSZ, &w) == -1) {
// If ioctl fails, it's not a tty
printf("%s is NOT a terminal (tty) or error occurred", argv[1]);
} else {
// If ioctl succeeds, it's a tty
printf("%s is a terminal (tty).\n", argv[1]);
}
printf("\nCheck for TTY via isatty()\n");
// Use isatty() to check if the file descriptor refers to a terminal
if (isatty(fd)) {
printf("%s is a terminal (tty).\n", argv[1]);
} else {
printf("%s is NOT a terminal (tty).\n", argv[1]);
}
// Close the device
close(fd);
return 0;
}
The result differs:
Check for TTY via ioctl(TIOCGWINSZ)
/dev/pts/0 is a terminal (tty).
Check for TTY via isatty()
/dev/pts/0 is a terminal (tty).
./check_tty_2604 /dev/pts/0
Check for TTY via ioctl(TIOCGWINSZ)
/dev/pts/0 is a terminal (tty).
Check for TTY via isatty()
/dev/pts/0 is NOT a terminal (tty).
So the proble seems to be in function isatty() which is implemente in
glibc.
glibc 2.41 and 2.42 show the following difference:
2.41:
__tcgetattr (int fd, struct termios *termios_p)
retval = INLINE_SYSCALL (ioctl, 3, fd, TCGETS, &k_termios);
2.42:
__tcgetattr (int fd, struct termios *termios_p)
long int retval = INLINE_SYSCALL_CALL (ioctl, fd, TCGETS2, &k_termios);
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https://bugs.launchpad.net/bugs/2133188
Title:
Illegal instruction in memset under qemu-user for riscv64
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