VSCode: Failed to launch: could not launch process: not an executable file

[firelizzard18]

What version of Delve are you using (dlv version)?

1.25.2; build af3df277866d7175e816eab14e56611053d4cdea

What version of Go are you using? (go version)?

go version go1.25.3 X:nodwarf5 linux/amd64

What operating system and processor architecture are you using?

Gentoo Linux 6.12.41, Intel x86_64, Wayland, KDE

Description

Sometimes when I attempt to launch my executable via VSCode I get this error message:

Debug console:

Starting: $GOBIN/dlv dap --listen=127.0.0.1:42255 --log-dest=3 from /my/executable
DAP server listening at: 127.0.0.1:42255

In this particular case, my debug configuration is:

        {
            "name": "Run",
            "type": "go",
            "request": "launch",
            "mode": "auto",
            "program": "${workspaceFolder}"
        }

But I've had this happen for many different configurations and I haven't been able to identify a parameter that triggers this. Part of the issue is that it happens more or less randomly; that is, I can't intentionally reproduce it. It just happens, whenever the gremlins in my computer feel like it.

If I change launch.json at all I'm able to launch again. Just now, I added then deleted white space (outside of any property or string), saved the file, and the error stopped happening. So there's definitely something weird happening, potentially related to vscode-go. I'm assuming this error report is not enough information to do anything about it; I guess I'm really asking for help/advice on how to debug this. I tried launching delve with delve, but that did not reproduce the issue. Also I haven't been able to reproduce the issue by directly launching with delve. Certainly the issue could be related to vscode-go, but I imagine it could also be some subtle caching issue, or something related to DAP mode, or all of the above. I've tried launching separately DAP mode then having vscode-go attach to that existing session, but I wasn't able to get that to work and I'm not sure it would reproduce the issue. Should I create a custom build/install of delve that includes debugging symbols and is unoptimized? Is it possible to tell delve to pause until a debugger attaches to it?

[aarzilli]

That error should come from the verifyBinaryFormat function in service/debugger/debugger.go. It just tries to open the file as an elf file (in your case). It sounds like the compiler produced a malformed executable, altough I don't know how it can be possible. You could change the function Remove in pkg/gobuild/gobuild.go to do nothing and when the bug happens examine the binary file that delve produced manually.

[firelizzard18]

The file was empty:

❯ file /home/firelizzard/src/game/loki/examples/bunnymark/__debug_bin3276119739
/home/firelizzard/src/game/loki/examples/bunnymark/__debug_bin3276119739: empty
❯ ll /home/firelizzard/src/game/loki/examples/bunnymark/__debug_bin3276119739
-rw------- 1 firelizzard firelizzard 0 Feb  9 18:30 /home/firelizzard/src/game/loki/examples/bunnymark/__debug_bin3276119739

I updated gocommandCombinedOutput to print out the output of the build command, but by the time I got that done it went back to working normally. There appears to be a correlation between "I just renamed a folder and had to update a bunch of imports" and the issue occurring, but of course as soon as I try to reproduce it on demand, it stops failing.

[aarzilli]

This sounds more like something in your environment (filesystems, antivirus, security software...) than delve's fault.

[firelizzard18]

I'm just running Gentoo on XFS, no extra AV, no weird filesystem shenanigans. I'm assuming something weird is going on with the go build command, hence printing the output. But I haven't had the issue recur since I added that.

[firelizzard18]

This appears to be a vscode/vscode-go bug. It reared it's head again and I was able to capture the launch request vscode sent, as well as the command that delve executed:

Got launch request: {"seq":2,"type":"request","command":"launch","arguments":{"name":"Crawl","type":"go","request":"launch","mode":"test","program":".","cwd":"/home/firelizzard/src/game/loki/examples/crawl","env":{"GOPATH":"/home/firelizzard/go","DEBUG_DELVE":"true"},"__configurationTarget":6,"packagePathToGoModPathMap":{},"debugAdapter":"dlv-dap","showRegisters":false,"showGlobalVariables":false,"substitutePath":[],"showLog":false,"logOutput":"debugger","dlvFlags":[],"hideSystemGoroutines":false,"dlvToolPath":"/home/firelizzard/go/bin/dlv","__buildDir":"/home/firelizzard/src/game/loki/examples/crawl","__sessionId":"695aea61-e3cc-4bef-9f4e-1abebc388434"}}

Executing (2) go test [-c -o /home/firelizzard/src/game/loki/examples/crawl/__debug_bin3125545199 -gcflags all=-N -l .]
Output
 ?   	codeberg.org/firelizzard/loki/examples/crawl	[no test files]

Not deleting the file: /home/firelizzard/src/game/loki/examples/crawl/__debug_bin3125545199

Side note - it would be nice if delve reported something more helpful than "Failed to launch: could not launch process: not an executable file" in this scenario (when attempting to go-test a package that doesn't have tests). FWIW, -json works on go test -c invocations, though it essentially just emits the same thing.

[firelizzard18]

The issue appears to be "mode": "auto". vscode-go incorrectly infers that I want to dlv test if I have a test file open, even though the actual launch configuration should preclude that. In light of that, I'm going to close this issue.

[aarzilli]

Reopening for better error message.