Regression in 1.30.x: aarch64 debug session hangs before main, *stopped notification for solib-event lost between GDB and MIEngine

[cangursu]

Environment

• OS and version:
  macOS Tahoe Version 26.4.1 (25E253)

• VS Code:
  Visual Studio Code

Version: 1.120.0 (Universal)
Commit: 0958016b2af9f09bb4257e0df4a95e2f90590f9f
Date: 2026-05-12T20:17:22Z (7 days ago)
Electron: 39.8.8
ElectronBuildId: 13870025
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Darwin arm64 25.4.0

• C/C++ extension:
  C/C++ for Visual Studio Code () - 1.32.2

• OS and version of remote machine (if applicable):
  Distributor ID: Ubuntu
  Description: Ubuntu 24.04.4 LTS
  Release: 24.04
  Codename: noble

• GDB / LLDB version:
  GNU gdb (Ubuntu 15.1-1ubuntu1~24.04.1) 15.1
  Copyright (C) 2024 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

Bug Summary and Steps to Reproduce

After updating the C/C++ extension to 1.30.3, debug sessions on aarch64 Linux hang immediately after -exec-run and never reach main. Downgrading to 1.29.3 with the same launch.json and the same container resolves the issue.
Environment

Host: macOS (Apple Silicon, M5 MacBook Pro)
Container: Ubuntu 24.04 LTS, aarch64, running on Docker
VSCode workflow: Remote-SSH into the container
GDB: GNU gdb (Ubuntu 15.1-1ubuntu1~24.04.1) 15.1, configured as aarch64-linux-gnu
C/C++ extension: 1.30.3 (broken), 1.29.3 (works)
MIEngine version reported in telemetry: 17.12.40402.1

Steps to reproduce

In a Docker container running aarch64 Ubuntu 24.04 with GDB 15.1, build any C++ binary with debug symbols.
Use a standard cppdbg launch configuration with MIMode: "gdb", request: "launch", no miDebuggerServerAddress (i.e., local launch via MIEngine's integrated-terminal mechanism).
Start the debug session.

Expected
Debugger stops at main (or at the first user breakpoint).
Actual
Session hangs indefinitely after -exec-run. The inferior process is started (=thread-group-started is visible in the engine log), the dynamic loader is reported (=library-loaded for /lib/ld-linux-aarch64.so.1), and then all subsequent MI commands from MIEngine go unanswered. main is never hit. From the user's perspective, no breakpoint fires.
Root cause (from engine log analysis)
MIEngine sets stop-on-solib-events 1 during initialisation. After -exec-run, GDB stops the inferior at the dynamic loader's solib-event as expected. However, the *stopped,reason="solib-event" notification appears to be lost between GDB and MIEngine: MIEngine's internal state remains "running", and typing -exec-continue in the Debug Console returns:

Unable to perform this action because the process is running.

So MIEngine never sees the stop, never issues the -exec-continue that would let GDB walk through subsequent library loads to main, and the session is wedged. The TTY warning visible in the integrated terminal (warning: GDB: Failed to set controlling terminal: Operation not permitted) is unrelated — it appears in both 1.29.3 (working) and 1.30.3 (broken) and does not affect execution.
What I tried

Disabling debuginfod via ~/.gdbinit and setupCommands → no change.
set inferior-tty /dev/null, set startup-with-shell off → no change.
Adding targetArchitecture: "arm64" to launch.json → fixes the assumed x86_64 warning, no effect on hang.
Manual gdb ./binary followed by start in the same container → works perfectly, hits main. So the container, GDB, ptrace, and the binary are all fine.
Downgrading the C/C++ extension to 1.29.3 (no other changes) → fixes the hang. main is hit normally.

Attachments
I can attach an engine log captured with:
json"logging": {
"engineLogging": true,
"trace": true,
"traceResponse": true
}
The relevant tail shows <-1025-exec-run followed by =thread-group-started, =thread-created, six =breakpoint-modified events, =library-loaded for ld-linux-aarch64.so.1, then five queued -symbol-list-lines commands with no responses. No *stopped event ever appears.

Debugger Configurations

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": "Mac - Exch Gateway Server SHM",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_server_shm",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "lldb"
        },
        {
            "name": "Mac - Exch Gateway FT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_ft",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "lldb"
        },
        {
            "name": "Exch Gateway Server UDP",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_server_udp",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Gateway Server SHM",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_server_shm",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Gateway Client",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_client",
            "args": ["127.0.0.1"],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Gateway FT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_ft",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Gateway UT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/app_exch_gateway_ut",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Binance UT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/exch_binance_ut",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Binance FT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/exch_binance_ft",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Exch Binance FT - Metrics",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/exch_binance_ft_binance_metrics",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Utils FT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/utils_ft",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Utils UT",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/utils_ut",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Sock Echo Server UDP",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/server_echo_udp",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        },
        {
            "name": "Sock Echo Client UDP",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/bin/client_echo_udp",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "CMake: build",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description": "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        }

    ]
}


task.json : 

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "cmake",
			"label": "CMake: build",
			"command": "build",
			"targets": [
				"all"
			],
			"group": "build",
			"problemMatcher": [],
			"detail": "CMake template build task"
		}
	]
}

Debugger Logs

--- LaunchOptions ---

LaunchOptions{"name":"Exch Gateway Server SHM","type":"cppdbg","request":"launch",
"program":"/wsDocker/exgw/exgw_exch_gateway/bin/app_exch_gateway_server_shm",
"args":[],"stopAtEntry":false,"cwd":"/wsDocker/exgw/exgw_exch_gateway",
"environment":[],"externalConsole":false,"MIMode":"gdb",
"preLaunchTask":"CMake: build",
"logging":{"engineLogging":true,"trace":true,"traceResponse":true},
"setupCommands":[
  {"description":"Enable pretty-printing for gdb","text":"-enable-pretty-printing","ignoreFailures":true},
  {"description":"Set Disassembly Flavor to Intel","text":"-gdb-set disassembly-flavor intel","ignoreFailures":true}
]}

--- GDB banner ---

GNU gdb (Ubuntu 15.1-1ubuntu1~24.04.1) 15.1
This GDB was configured as "aarch64-linux-gnu".

--- MIEngine telemetry ---

EngineVersion: 17.12.40402.1
HostVersion:   17.12.40402.1
AdapterId:     cppdbg
MIMode:        gdb

--- MIEngine misdetects architecture as x86_64 even though GDB reports aarch64 ---

stdout: Warning: Debuggee TargetArchitecture not detected, assuming x86_64.

--- After -exec-run: process starts, dynamic loader loads, then session hangs ---

<-1022-exec-run
->&"warning: Error disabling address space randomization: Operation not permitted\n"
->=thread-group-started,id="i1",pid="12275"
->=thread-created,id="1",group-id="i1"
<-1023-thread-info 1
->=breakpoint-modified,bkpt={number="1",...addr="0x0000aaaadedcb608",func="main(int, char* const*)",...}
->=breakpoint-modified,bkpt={number="2",...}
->=breakpoint-modified,bkpt={number="3",...}
->=breakpoint-modified,bkpt={number="4",...}
->=breakpoint-modified,bkpt={number="5",...}
->=breakpoint-modified,bkpt={number="6",...}
->=library-loaded,id="/lib/ld-linux-aarch64.so.1",symbols-loaded="0",...
<-1024-symbol-list-lines .../main_shm.cpp
<-1025-symbol-list-lines .../main_shm.cpp
<-1026-symbol-list-lines .../main.cpp
<-1027-symbol-list-lines .../server_exgw.hpp
<-1028-symbol-list-lines .../server_exgw.hpp
->~"Downloading separate debug info for system-supplied DSO at 0xffffb849e000...\n"

[session never reaches main; no response to commands 1023-1028; no *stopped event ever delivered]

<--   C (disconnect-14): user-initiated disconnect

Other Extensions

No response

Additional Information

vscode_cppext_regression.txt

[sean-mcmanus]

@cangursu This sounds like a bug with MIEngine, which got updated in that release. Can you file a bug at https://github.com/microsoft/MIEngine/issues ? I can't seem to transfer this bug there. Or I could open it there myself.