vscode bazel debug c++ doesn't work

[pyrl247]

Hello,I have a cpp project and build with bazel,when I set breakpoint ,the point turns grey immediately;but I can use command lldb to debug my bazel build binary and set breakpoint correctly.
Here is my launch.json.

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Debug",
            "program": "${workspaceFolder}/bazel-bin/source/main",
            "args": [],
            "cwd": "${workspaceFolder}",
            "MIMode": "lldb",
        }
    ]
}

My bazel build command is "bazel build --repo_env=CC=clang --copt="-g" --strip=never -c dbg --sandbox_debug //source:main"
I have turn on the debuglog for lldb,when I set a breakpoint ,it shows like this:

{"variables":[{"evaluateName":"a","memoryReference":"0x7FFEEFBFF440","name":"a","type":"A","value":"{...}","variablesReference":1016}]}}
[2021-09-15T05:57:09.054Z DEBUG codelldb::dap_codec] --> {"command":"setBreakpoints","arguments":{"source":{"name":"main.cc","path":"/Users/pyrl/work/vscode/bazelbuild/source/main.cc"},"lines":[12,13],"breakpoints":[{"line":12},{"line":13}],"sourceModified":false},"type":"request","seq":18}
[2021-09-15T05:57:09.056Z DEBUG codelldb::debug_session] Debug event: 0x7ffcca4dd428 Event: broadcaster = 0x7ffccc01b440 (lldb.target), type = 0x00000001 (breakpoint-changed), data = {}
[2021-09-15T05:57:09.056Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":18,"success":true,"command":"setBreakpoints","body":{"breakpoints":[{"id":1,"message":"Resolved locations: 0","verified":false},{"id":3,"message":"Resolved locations: 0","verified":false}]}}

Any help will be appreciate.

[vadimcn]

Bazel replaces the actual source location with "/proc/self/cwd" in order to achieve repeatable builds.
You'll need to add "sourceMap": { "/proc/self/cwd": "${workspaceFolder}" } to your launch configuration.

Edit: "sourceMap": { ".": "${workspaceFolder}" } on OSX and Windows.

[pyrl247]

I am using macos ,doesn't have /proc in my system.

[vadimcn]

Not sure what it does on OSX, but I'd expect something similar. Try setting a function breakpoint (or set "stopOnEntry": true), and when it breaks, use debug_info LLDB command to find out what path is encoded in the debug info. Also, see this.

[pyrl247]

I can break through method name,then I print the "source info" in my lldb consul , the output shows:

source info
Lines found in module `main
[0x000000010000364f-0x0000000100003660): source/main.cc:10:5

The relative path is correct with my workspaceFolder;but still can't break through line in vscode.

[vadimcn]

Try "sourceMap": { ".": "${workspaceFolder}" }

[pyrl247]

It works!!! Thank u so much!!!!

[art-bochkarev]

@vadimcn I have similar troubles with Bazel. But this solution doesn't help. Even adding {"stopAtEntry": true} doesn't pause the execution on start. I'm trying to run one of the UnitTests and it have very strange path to the executable. Could it be trouble with path or should stopAtEntry be hit even with wrong paths inside "sourceMap"?

[vadimcn]

In my experience, stopAtEntry always works, assuming the debugger has managed to find and launch the debuggee.

[gedalia]

I had to do:
"sourceFileMap": { "/proc/self/cwd": "${workspaceFolder}/.." },
not sure if there's a way to get externals to work at the same time.

[jfirebaugh]

On macOS, in addition to the sourceMap setting, you will need to build with --features=oso_prefix_is_pwd and have platform settings -w $execution_root in your lldb init script, where $execution_root is the Bazel execution root (what bazel info execution_root prints).

[aminya]

The following works for both lldb and cppdbg :

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "cppdbg",
            "request": "launch",
            "name": "Launch",
            "cwd": "${workspaceRoot}",
            "program": "${workspaceRoot}/bazel-bin/main",
            "args": [],
            "sourceFileMap": {
                "proc/self/cwd": "{workspaceFolder}",
                ".": "${workspaceFolder}"
            }
        },
        {
            "type": "lldb",
            "request": "launch",
            "name": "Launch LLDB",
            "cwd": "${workspaceRoot}",
            "program": "${workspaceRoot}/bazel-bin/main",
            "args": [],
            "sourceMap": {
                "proc/self/cwd": "{workspaceFolder}",
                ".": "${workspaceFolder}"
            }
        }
    ]
}