Vscode-cpptools: Failed to open /dev/tty with vscode debugger

[0w0miki]

In my program, I tried to read /dev/tty. The program cannot open the file with vscode debugger, but the file is successfully opened with gdb command line.

The source code is:

#include <stdio.h>
#include <fcntl.h>

int main(int argc, char const *argv[])
{
    int f = open("/dev/tty", O_RDONLY);
    printf("open tty %d\n",f);
    return 0;
}

The program is then build with g++ -g ./main.cpp.

When I use gdb to debug in vscode, it gives:

open tty -1

However, with command line gdb ./a.out, the file can be open successfully.

(gdb) r
Starting program: /home/miki0w0/c_test/a.out
open tty 3
[Inferior 1 (process 22818) exited normally]
(gdb) q

A same open issue can be found at https://stackoverflow.com/questions/52027368/unable-to-open-dev-ttyusb0-while-debugging-with-visual-studio-code-on-linux.

The vscode debugger works well in other cases. I wounder what causes the difference and how to fix it.

The environment is:

• OS and Version: Ubuntu 16.04
• VS Code Version: 1.32.3
• C/C++ Extension Version: 0.22.1
• Other extensions you installed (and if the issue persists after disabling them): None

Additional context
My configure file is:
launch.json.txt.

And the log information is included in this file:
debuglog.txt

[pieandcakes]

Can you add errno to your printf statement to see what the actual error is? I wonder if it is a permissions issue but would need to know more about why its failing.

For reference: http://man7.org/linux/man-pages/man3/errno.3.html

[0w0miki]

Can you add errno to your printf statement to see what the actual error is? I wonder if it is a permissions issue but would need to know more about why its failing.

For reference: http://man7.org/linux/man-pages/man3/errno.3.html

I added errno to the code, and the following are the results with VS code debugger and gdb command line.
Using debugger, the output is:

errno: 6
No such device or address
open tty -1

Using gdb ./a.out, the output is:

errno: 0
Success
open tty 3

The code is modified as

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

int main(int argc, char const *argv[])
{
    errno = 0;
    int f = open("/dev/tty", O_RDONLY);
    int errsv = errno;
    printf("errno: %d\n", errsv);
    printf("%s\n",strerror(errsv));
    printf("open tty %d\n",f);
    return 0;
}

[osa1]

Just came here to report this -- would be good to see this fixed as this makes debugging TUI apps in vscode quite hard.

[gerekon]

I have the same issue, but with opening regular file for writing. Debugging with GDB from command line works well.
Errno code is "No such file or directory".
I use Ubuntu 18.04

[remicorniere]

Came here to report the same thing. It makes TUI apps impossible to debug.

[nojus297]

Same issue (with GO debugger)

[goto3k]

Having the same issue:
fd = open("/dev/tty", O_RDWR, 0);

fd=-1
errno=6 (No such device or address),

[pieandcakes]

@WardenGnaw

[github-actions[bot]]

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