microsoft / microsoft/vscode-cpptools

C++ Debug breakpoint doesn't work with linked libraries built with the application in VSCode when using `-Og` compilation flag/option.

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debugger help wanted
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Description

Environment
  • OS and version: Ubuntu 25.10
  • VS Code: 1.114.0
  • C/C++ extension: 1.5.1
  • OS and version of remote machine (if applicable):
  • GDB / LLDB version: 16.3
Bug Summary and Steps to Reproduce

Bug Summary:
Breakpoints set inside a statically linked library built with the same C++ application in the same source tree are greyed out and not hit.

Steps to reproduce:
Console.cpp CMakeLists.txt:

target_link_libraries(${PROJECT_NAME} PRIVATE
MyLibrary.Core
)

top-level CMakeLists.txt:

set(CMAKE_CXX_STANDARD 26)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(CMAKE_BUILD_TYPE "Debug")

# ###############################################################################
# Global compiler options
# https://stackoverflow.com/questions/79444534/vscode-cmake-configure-does-not-generate-cmakecache-txt-from-cmakelists-txt
# CMAKE_CXX_COMPILER_ID is set only at the project() call, when CMake actually detect compilers.
# ###############################################################################
if(MSVC)
    # remove default flags provided with CMake for MSVC
    set(CMAKE_CXX_FLAGS "")
    set(CMAKE_CXX_FLAGS_DEBUG "")
    set(CMAKE_CXX_FLAGS_RELEASE "")
elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
    message("-- Setting GNU options from CMakeLists.txt")
    set(CMAKE_CXX_FLAGS "-std=gnu++26 -fdiagnostics-color=always" CACHE STRING "CXX build flags" FORCE)
    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS} -ggdb3 -Og -g3" CACHE STRING "Debug build flags" FORCE)
    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS} -O3 -DNDEBUG" CACHE STRING "Release build flags" FORCE)
endif()
Debugger Configurations

launch.json:

        {
            "name": "C++ Launch (Console)",
            "type": "cppdbg",
            "request": "launch",
            "preLaunchTask": "CMake: build all",
            "postDebugTask": "",
            "program": "${workspaceFolder}/Debug/Console",
            "cwd": "${workspaceFolder}/build",
            "stopAtEntry": false,
            "externalConsole": false,
            "launchCompleteCommand": "exec-run",
            "linux": {
              "MIMode": "gdb",
              "miDebuggerPath": "/usr/bin/gdb"
            },
            "osx": {
              "MIMode": "lldb"
            },
            "windows": {
              "MIMode": "gdb",
              "miDebuggerPath": "C:\\MinGw\\bin\\gdb.exe"
            },
            "args": [],
            "setupCommands": [
                {
                    "description": "Disable MI-async",
                    "text": "set mi-async off",
                    "ignoreFailures": true
                },
                {
                    "description": "Enable auto-load for all paths. Considered a security risk. See link for details: https://sourceware.org/gdb/current/onlinedocs/gdb.html/Auto_002dloading-safe-path.html",
                    "text": "set auto-load safe-path /",
                    "ignoreFailures": true
                },
                {
                    "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
                },                
                {
                    "description": "Do not display function arguments when printing a stack frame",
                    "text": "set print frame-arguments none",
                    "ignoreFailures": true
                }
            ]
        },          

tasks.json:

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "cmake",
			"label": "CMake: build all",
			"command": "build",
			"targets": [
				"all"
			],
			"group": {
				"kind": "build",
				"isDefault": true
			},
			"problemMatcher": ["$gcc"],
			"detail": "CMake build all"
		},
		{
			"type": "cmake",
			"label": "CMake: build Console",
			"command": "build",
			"targets": [
				"Console"
			],
			"group": {
				"kind": "build",
				"isDefault": false
			},
			"problemMatcher": ["$gcc"],
			"detail": "CMake build Console"
		},
		{
			"type": "cmake",
			"label": "CMake: build Core",
			"command": "build",
			"targets": [
				"DataStructuresAlgorithms.Core"
			],
			"group": {
				"kind": "build",
				"isDefault": false
			},
			"problemMatcher": ["$gcc"],
			"detail": "CMake build Core"
		},
		{
			"type": "cmake",
			"label": "CMake: build Tests",
			"command": "build",
			"targets": [
				"DataStructuresAlgorithms.Tests"
			],
			"group": {
				"kind": "build",
				"isDefault": false
			},
			"problemMatcher": ["$gcc"],
			"detail": "CMake build Tests"
		},
	]
}
Debugger Logs
--> E (output): {"type":"event","event":"output","body":{"category":"console","output":"1: (590) DebuggerPid=583206\n"},"seq":185}
1: (590) DebuggerPid=583206
<--   C (setBreakpoints-4): {"command":"setBreakpoints","arguments":{"source":{"name":"Arithmetic.cpp","path":"/usr/src/DataStructuresAlgorithms/src/Arithmetic.cpp"},"lines":[299,323],"breakpoints":[{"line":299},{"line":323}],"sourceModified":false},"type":"request","seq":4}
--> E (output): {"type":"event","event":"output","body":{"category":"console","output":"1: (604) <-1016-break-insert -f Arithmetic.cpp:299\n"},"seq":188}
1: (604) <-1016-break-insert -f Arithmetic.cpp:299
--> E (output): {"type":"event","event":"output","body":{"category":"console","output":"1: (701) ->&\"No compiled code for line 299 in file \\\"Arithmetic.cpp\\\".\\n\"\n"},"seq":190}
1: (701) ->&"No compiled code for line 299 in file \"Arithmetic.cpp\".\n"
--> E (output): {"type":"event","event":"output","body":{"category":"console","output":"1: (702) ->1016^done,bkpt={number=\"2\",type=\"breakpoint\",disp=\"keep\",enabled=\"y\",addr=\"<PENDING>\",pending=\"Arithmetic.cpp:299\",times=\"0\",original-location=\"Arithmetic.cpp:299\"}\n"},"seq":192}
1: (702) ->1016^done,bkpt={number="2",type="breakpoint",disp="keep",enabled="y",addr="<PENDING>",pending="Arithmetic.cpp:299",times="0",original-location="Arithmetic.cpp:299"}
--> E (output): {"type":"event","event":"output","body":{"category":"console","output":"1: (702) ->(gdb)\n"},"seq":194}
Other Extensions

No response

Additional Information

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Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the supplied launch.json, tasks.json, and top-level CMakeLists.txt, then reproduce the pending breakpoint for Arithmetic.cpp:299 using GDB and the -Og flags. Compare the debugger logs while building the Console and DataStructuresAlgorithms.Core targets; done means the breakpoint resolves to compiled code and is hit inside the statically linked library.

Written by the indexing model from the issue text.

Assessment

Tech stack
cmake, cpp, vscode
Domain
build-system, developer-experience, devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
45/100

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