🪵 Dumping JavaScript Engine Logs in iBrowe

If you need to capture internal logs from the JavaScript engine (V8) when running iBrowe, you can use logging flags during launch. This is useful for debugging low-level V8 behaviors.

🚀 Launching iBrowe with Logging Enabled

ibrowe --no-sandbox --js-flags="--log-all --log-file=/path/to/logs/%t.log"

This command enables full logging and outputs logs to a file where %t is replaced with the current timestamp.


🧩 Log File Placeholders

You can customize the log filename using these placeholders:

  • %p: current process ID
  • %t: current timestamp (in milliseconds)

🔗 Reference: https://github.com/v8/v8/blob/a802d5aae5a28f7b762d836429d7c1d4da98537e/src/logging/log.cc#L2107-L2114


🎯 Useful V8 Logging Flags

Besides --log-all, here are additional flags to help filter output:

  • --log-code
  • --log-function-events
  • --log-timer-events
  • --log-snapshot-positions
  • --log-source-code
  • --log-maps

Full flag definitions: https://github.com/v8/v8/blob/a802d5aae5a28f7b762d836429d7c1d4da98537e/src/flags/flag-definitions.h#L2207-L2229


🧵 Custom Logging (C++ - printf-style)

For advanced debugging, you can log messages manually from C++:

#include "src/strings/string-stream.h"

HeapStringAllocator allocator;
StringStream strstream(&allocator);
strstream.Add("hello log %d", int_value);
strstream.Log(isolate);

This allows for dynamic formatting and outputting directly into the log stream tied to the V8 isolate.


Adapted from Brave documentation and V8 source references: https://github.com/v8/v8 https://github.com/brave/brave-browser