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Panic Recovery Test

v2/examples/panic-recovery-test/README.md

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Panic Recovery Test

This example demonstrates the Linux signal handler issue (#3965) and verifies the fix using runtime.ResetSignalHandlers().

The Problem

On Linux, WebKit installs signal handlers without the SA_ONSTACK flag, which prevents Go from recovering panics caused by nil pointer dereferences (SIGSEGV). Without the fix, the application crashes with:

signal 11 received but handler not on signal stack
fatal error: non-Go code set up signal handler without SA_ONSTACK flag

The Solution

Call runtime.ResetSignalHandlers() immediately before code that might panic:

go
import "github.com/wailsapp/wails/v2/pkg/runtime"

go func() {
    defer func() {
        if err := recover(); err != nil {
            log.Printf("Recovered: %v", err)
        }
    }()
    runtime.ResetSignalHandlers()
    // Code that might panic...
}()

How to Reproduce

Prerequisites

  • Linux with WebKit2GTK 4.1 installed
  • Go 1.21+
  • Wails CLI

Steps

  1. Build the example:

    bash
    cd v2/examples/panic-recovery-test
wails build -tags webkit2_41

  2. Run the application:

    bash
    ./build/bin/panic-recovery-test

  3. Wait ~10 seconds (the app auto-calls Greet after 5s, then waits another 5s before the nil pointer dereference)

Expected Result (with fix)

The panic is recovered and you see:

------------------------------"invalid memory address or nil pointer dereference"

The application continues running.

Without the fix

Comment out the runtime.ResetSignalHandlers() call in app.go and rebuild. The application will crash with a fatal signal 11 error.

Files

  • app.go - Contains the Greet function that demonstrates panic recovery
  • frontend/src/main.js - Auto-calls Greet after 5 seconds to trigger the test