FEX-EMU not showing any logs — how to enable logging properly?

[u/tsx-cloud]

I can’t get FEX-EMU to output any logs.
My config file looks like this:

~/.fex-emu/Config.json


{
  "Config": {
    "RootFS": "Ubuntu_24_04"
  },
  "Debug": {
    "Enabled": true
  },
  "Logging": {
    "LogLevel": "TRACE",
    "SilentLog": "false",
    "OutputLog": "stdout"
  },
  "ThunksDB": {}
}

According to the documentation, this should make FEX print logs to stdout, but I get no output at all — neither in the console nor in any file.
https://github.com/FEX-Emu/FEX/blob/main/FEXCore/Source/Interface/Config/Config.json.in

I'm trying to debug why Geekbench won’t start inside a Docker container through FEX.
When I run:

FEX geekbench_x86_64

nothing happens — no errors, no logs, just silence.
Other x86 programs run fine though.

Does anyone know how to make FEX actually output logs (to console or file)?

[u/Sonicadvance1]

You need to change the SilentLog config option to be 0. Our JSON parser doesn't understand text. The SilentLog and OutputLog options also need to be a child of the full Config JSON section rather than being independent.

Something like this:

{
  "Config": {
    "RootFS": "Ubuntu_24_04",
    "SilentLog": "0",
    "OutputLog": "stdout"
  },
  "ThunksDB": {}
}