GDB in Visual Studio Code doesn't show printf() output to stdout

Question

When debugging a C project in VSCode with GDB, the output to stdout (through printf()) does not appear on the Debug Console. When using cppvsdebug, however, it works.

This is my launch.json:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
        "version": "0.2.0",
        "configurations": [
          {
            "name": "Debug",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/${fileBasenameNoExtension}",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
              {
                "description": "Enable pretty-printing for gdb",
                "text": "-enable-pretty-printing",
                "ignoreFailures": false
              }
            ],
            "windows": {
              "miDebuggerPath": "C:/raylib/mingw/bin/gdb.exe",
            },
            "osx": {
              "MIMode": "lldb"
            },
            "linux": {
              "miDebuggerPath": "/usr/bin/gdb",
            },
            "preLaunchTask": "build debug"
          },
          {
            "name": "Run",
            "type": "cppdbg",
            "request": "launch",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "program": "${workspaceFolder}/main",
            "MIMode": "gdb",
            "windows": {
              "program": "${workspaceFolder}/main.exe",
              "miDebuggerPath": "C:/raylib/mingw/bin/gdb.exe"
            },
            "osx": {
              "MIMode": "lldb"
            },
            "linux": {
              "miDebuggerPath": "/usr/bin/gdb"
            },
            "preLaunchTask": "build release",
          }
        ]
      }

This is the command that is executed to run the debug session (according to the terminal window):

'c:\Users\...\.vscode\extensions\ms-vscode.cpptools-0.27.1\debugAdapters\bin\WindowsDebugLauncher.exe' '--stdin=Microsoft-MIEngine-In-2dvbqvix.1cb' '--stdout=Microsoft-MIEngine-Out-1m5j1iy0.ufe' '--stderr=Microsoft-MIEngine-Error-oqyothgz.h5l' '--pid=Microsoft-MIEngine-Pid-hal3wx4b.uld' '--dbgExe=C:/raylib/mingw/bin/gdb.exe' '--interpreter=mi'

The Debug Console shows the "splash screen" info of GDB, but doesn't display any of the output from the printf() statements in my code:

=thread-group-added,id="i1"
GNU gdb (GDB) 8.1
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-w64-mingw32".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
Warning: Debuggee TargetArchitecture not detected, assuming x86_64.
=cmd-param-changed,param="pagination",value="off"
[New Thread 9488.0x54dc]
[New Thread 9488.0x577c]
[New Thread 9488.0xff4]
[New Thread 9488.0x4918]

When I run the Exe file with GDB from the commandline (Git Bash), all the output is displayed normally.

Setting externalConsole to true doesn't work (it also doesn't open an external console to begin with).

I'm on Windows 10.

Is there any specific setting I need to adjust for this to work?

Perhaps you should fflush(stdout) in the code for the output to be shown. Especially if there is no newline at the end of the printf output. — Weather Vane
The minimal example should be printf("Hello, World!\n"); Does that work? — stark
@Weather Vane Calling fflush() doesn't work.As I mentioned, it also works perfectly fine when using GDB from the commandline directly. So I am pretty sure that it has something to do with Visual Studio Code. — MontyHimself
You can try to reload your gcc compiler. Check the mingw-w64 version and download the latest version for your vscode. — lifanxin

Kfir Ben Shimon Kfir Ben Shimon · Accepted Answer · 2020-11-25T10:07:58

0

votes

Setting "externalConsole" to true solved the issue for me.

GDB in Visual Studio Code doesn't show printf() output to stdout

3 Answers