Native GDB DAP unable to run

[ibsil]

Debug adapter definition and debug configuration

I have installed nvim-dap, and nvim-dap-ui and GDB 14.2 which should have DAP included. I have also written a simple C program main.c for testing that nvim-dap is working as expected.

// main.c
#include "stdio.h"
int main(){
int x = 0;
x = x+1;
printf("%d",x);
}

In my init.lua I have written the dap configuration as follows:

require('dap').adapters.gdb = {
  type = "executable",
  command = "gdb",
  args = { "-i", "dap" }
}
require('dap').configurations.c = {
  {
    name = "Launch",
    type = "gdb",
    request = "launch",
    program = function()
      return vim.fn.input('Path to executable: ', vim.fn.getcwd() .. '/', 'file')
    end,
    cwd = "${workspaceFolder}",
    stopAtBeginningOfMainSubprogram = false,
  },
}
require("dapui").setup()

The program main.c compiles and runs without issue.

Debug adapter version

No response

Steps to Reproduce

1. Compile main.c with gcc -ggdb main.c -o main
2. Open main.c and call :DapContinue, specify path to executable main
3. Errors can be seen in REPL with :DapToggleRepl

Expected Result

Expected dap-ui to bring up windows used to aid in debugging the program (program state, function call stack, expression watching, breakpoints, etc.)

Actual Result

GNU gdb (GDB) 14.2
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This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
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1Exception in thread DAP:
Traceback (most recent call last):
  File "/usr/lib/python3.12/threading.py", line 1073, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.12/threading.py", line 1010, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/share/gdb/python/gdb/dap/startup.py", line 51, in really_start_dap
    target()
  File "/usr/share/gdb/python/gdb/dap/startup.py", line 73, in ensure_dap_thread
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/share/gdb/python/gdb/dap/server.py", line 117, in main_loop
    cmd = read_json(self.in_stream)
          ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/share/gdb/python/gdb/dap/io.py", line 37, in read_json
    while len(data) < content_length:
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: '<' not supported between instances of 'int' and 'NoneType'

[curtishd]

I reproduce the issue, gdb shows rollout code as 1.

[kkcarlc]

I can also confirm that I have this same issue. Not using nvim-dap-ui.

gcc (GCC) 13.2.1 20240417 Python 3.12.3 pynvim 0.5.0

[mfussenegger]

Sounds like a duplicate of https://github.com/mfussenegger/nvim-dap/issues/1150 ?

Note that the error is printed when the debug session exits, and it stops fine at breakpoints and so on.

[kkcarlc]

@mfussenegger You are right. Thanks for answering.

You can disregard my comment since I was using a non supported version of gcc (13.2) and was not getting breakpoints which I wrongly correlated with the above message. I updated to gcc 14.1 today and it is indeed hitting breakpoints and the message printed is after the session exits as you stated.

[mfussenegger]

Changed the process shutdown logic a bit (https://github.com/mfussenegger/nvim-dap/pull/1210). It now closes the stdio handles after the process has exited, instead of doing that a bit earlier. That gets rid of the error messages in the repl.

[kkcarlc]

Thanks @mfussenegger I have confirmed the fix.