Fix memory leak in callbackRetText function

[hionay]

This PR fixes the memory leak in the callbackRetText function by freeing the memory allocated by the code:

C.CString(v.Interface().(string))

[Imran-imtiaz48]

Review

1. Safety and Memory Management:

   • The latest version introduces proper memory management by using defer C.free(unsafe.Pointer(cstr)) to ensure that the allocated C string is freed, preventing memory leaks. This is a significant improvement over the previous version, which did not free the allocated memory.

2. Readability and Maintainability:

   • Both versions are fairly readable and maintainable. However, the latest version's use of defer for freeing memory makes the intent clear and the code more idiomatic Go.

3. Error Handling:

   • The error handling for the type check is appropriate in both versions. However, you might want to include the actual type in the error message for better debugging.

Suggestions for Improvement

1. Enhanced Error Message:

   • Improve the error message to include the actual type of v. This will make debugging easier.
   • Example: return fmt.Errorf("cannot convert %s to TEXT, expected string", v.Type())

2. Use of unsafe.Pointer:

   • While the use of unsafe.Pointer is necessary here, always ensure that this is well-documented, as it can be error-prone if misused.

Revised Code with Suggested Improvements

if v.Type().Kind() != reflect.String {
	return fmt.Errorf("cannot convert %s to TEXT, expected string", v.Type())
}
cstr := C.CString(v.Interface().(string))
defer C.free(unsafe.Pointer(cstr))
C._sqlite3_result_text(ctx, cstr)
return nil

Conclusion

The latest version of the code is a good improvement over the previous version, particularly in terms of memory management. The suggested enhancement for the error message will further improve the code's clarity and debuggability.

[otoolep]

Real LLM vibes with that last review comment.

[hionay]

Hi @mattn, how can I help in getting this merged?

[charlievieth]

@mattn / @rittneje this is a pretty straightforward (and correct) fix for an obvious bug - could either of you take a look at this PR?