Failed to open /dev/tty with vscode debugger

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

Inizia confrontando i file allegati launch.json e debuglog.txt con l’invocazione di gdb dalla riga di comando, quindi esamina come il debugger C++ di VS Code avvia il programma e gli fornisce il terminale di controllo. Riproduci il problema sulla configurazione Ubuntu 16.04 indicata con il programma di esempio /dev/tty; il lavoro è completato quando l’esecuzione di debug di VS Code apre /dev/tty come l’esecuzione dalla riga di comando.