---
title: "BNNSGraphCompileOptionsSetMessageLogCallback(_:_:_:)"
framework: accelerate
role: symbol
role_heading: Function
path: "accelerate/bnnsgraphcompileoptionssetmessagelogcallback(_:_:_:)"
---

# BNNSGraphCompileOptionsSetMessageLogCallback(_:_:_:)

Specifies a customized callback function that reports compile-time messages.

## Declaration

```swift
func BNNSGraphCompileOptionsSetMessageLogCallback(_ options: bnns_graph_compile_options_t, _ log_callback: bnns_graph_compile_message_fn_t, _ additional_logging_arguments: UnsafeMutablePointer<bnns_user_message_data_t>?)
```

## Parameters

- `options`: The compilation options object.
- `log_callback`: The message-logging callback function.
- `additional_logging_arguments`: Additional data for the message-logging functions that BNNS passes unaltered to the callback function.

## Discussion

Discussion If you don’t specify this callback, default callback functions log messages to os_log. The following code adds a custom graph compile message callback function that prints BNNSGraphMessageLevelInfo level messages to the console: let options = BNNSGraphCompileOptionsMakeDefault() defer {     BNNSGraphCompileOptionsDestroy(options) }

BNNSGraphCompileOptionsSetMessageLogMask(options, BNNSGraphMessageLevelInfo.rawValue) BNNSGraphCompileOptionsSetMessageLogCallback(options, messageLogCallback, nil)

func messageLogCallback(msg_level: BNNSGraphMessageLevel,                         error_msg: UnsafePointer<CChar>,                         source_location: UnsafePointer<CChar>?,                         user_message_data_t:UnsafeMutablePointer<user_message_data_t>?) {          print(NSString(cString: error_msg, encoding: NSUTF8StringEncoding) ?? "")     if let source_location = source_location {         print(NSString(cString: source_location, encoding: NSUTF8StringEncoding) ?? "")     } }

## See Also

### Specifying a graph’s compile-time message callback

- [BNNSGraphCompileOptionsSetMessageLogMask(_:_:)](accelerate/bnnsgraphcompileoptionssetmessagelogmask(_:_:).md)
- [BNNSGraphContextSetMessageLogMask(_:_:)](accelerate/bnnsgraphcontextsetmessagelogmask(_:_:).md)
- [BNNSGraphMessageLevel](accelerate/bnnsgraphmessagelevel.md)
- [bnns_graph_compile_message_fn_t](accelerate/bnns_graph_compile_message_fn_t.md)
- [bnns_user_message_data_t](accelerate/bnns_user_message_data_t.md)