Ticker::once_ms() warning when used with argument

[mrengineer7777]

Board

ESP32 Feather

Device Description

Adafruit ESP32 Feather dev board

Hardware Configuration

No

Version

v2.0.2

IDE Name

PlatformIO in Visual Studio Code

Operating System

Win10

Flash frequency

N/A

PSRAM enabled

no

Upload speed

115200

Description

Compiling Ticker give me a warning.

Calling this works fine, no warning:
Save_Ticker.once_ms(ms, EP_Save);

Calling this results in a worrisome warning message:
WiFiCtrl.SoftAP_Shutdown_Timer.once_ms(1000*timeout_secs, ShutdownSoftAP, u);

The difference is that the callback function "ShutdownSoftAP" has a parameter "u". It is this parameter that the compiler complains about. It seems to be an issue with the template in Ticker.h.

Background:
I am compiling under native IDF because I need access to functions that don't exist yet in Arduino. I have copied in arduinoespressif\cores and arduinoespressif\library\Ticker. I did fix many circular include dependencies. I am NOT compiling Arduino as IDF component. Tried that, finally gave up.

Targeting: platform = https://github.com/tasmota/platform-espressif32/releases/download/v2.0.2idf/platform-espressif32-2.0.2.zip
This uses IDF 4.4, Arduino 2.0.2
https://github.com/tasmota/platform-espressif32/releases/tag/v2.0.2idf

Sketch

void WiFiCtrlClass::ScheduleSoftAPShutdownTimeSecs(uint32_t timeout_secs, bool DisconnectClients) {
  //Serial.printf("Scheduling SoftAP shutdown for %u secs\r\n", timeout_secs);

  uint32_t u;
  DisconnectClients == true ? u=1 : u=0;

  if(timeout_secs == 0)
    WiFiCtrl.SoftAP_Shutdown_Timer.detach();
  else
    WiFiCtrl.SoftAP_Shutdown_Timer.once_ms(1000*timeout_secs, ShutdownSoftAP, u);
}

void static ShutdownSoftAP(uint32_t disconnect_clients) {
  if(disconnect_clients==0 && WiFi.softAPgetStationNum()>0) {                         //Client is still connected. Try again in 1 minute.
      Serial.printf("ShutdownSoftAP() Clients=%u\r\n",WiFi.softAPgetStationNum());
      WiFiCtrl.ScheduleSoftAPShutdownTimeSecs(10, false);
      return;
    }
    //Serial.println("Shutting down SoftAP");
    WiFi.enableAP(false);
}

---From Ticker.h---
template<typename TArg>
  void once_ms(uint32_t milliseconds, void (*callback)(TArg), TArg arg)
  {
    static_assert(sizeof(TArg) <= sizeof(uint32_t), "attach_ms() callback argument size must be <= 4 bytes");
    uint32_t arg32 = (uint32_t)(arg);
    _attach_ms(milliseconds, false, reinterpret_cast<callback_with_arg_t>(callback), arg32);
  }

Debug Message

lib/Ticker/Ticker.h:92:37: warning: cast between incompatible function types from 'void (*)(unsigned int)' to 'Ticker::callback_with_arg_t' {aka 'void (*)(void*)'} [-Wcast-function-type]
     _attach_ms(milliseconds, false, reinterpret_cast<callback_with_arg_t>(callback), arg32);

It appears to be unhappy with casting (unsigned int) to (void*).

Other Steps to Reproduce

Originally my callback function had a Boolean parameter, but I changed it to uint32_t because the template casts it to uint32_t. I get pretty much the same warning.

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[mrengineer7777]

Possibly related: #2849
The proposed change modifies once_ms so that it no longer casts the argument.

template<typename TArg> void once_ms(uint64_t milliseconds, void (*callback)(TArg), TArg arg) { static_assert(sizeof(TArg) <= sizeof(void*), "attach() callback argument size must be <= sizeof(void*)"); _attach_us(1000ULL * milliseconds, false, reinterpret_cast<callback_with_arg_t>(callback), (void*)arg); }

Edit: just tested with modified library in #2849. It still gives the same warning :(

[VojtechBartoska]

Hello, can you please retest this on v2.0.3-rc1?

[mrengineer7777]

Retested, still fails. Not surprising since v2.0.3-rc1 didn't modify Ticker.h.

In file included from lib/WiFiCtrl/WiFiCtrl.h:4,
                 from lib/WiFiCtrl/WiFiCtrl.cpp:1:
lib/Ticker/Ticker.h: In instantiation of 'void Ticker::once_ms(uint32_t, void (*)(TArg), TArg) [with TArg = unsigned int; uint32_t = unsigned int]':
lib/WiFiCtrl/WiFiCtrl.cpp:541:80:   required from here
lib/Ticker/Ticker.h:92:37: warning: cast between incompatible function types from 'void (*)(unsigned int)' to 'Ticker::callback_with_arg_t' {aka 'void (*)(void*)'} [-Wcast-function-type]
     _attach_ms(milliseconds, false, reinterpret_cast<callback_with_arg_t>(callback), arg32);

Setup: VSCode with Platformio.
platformio.ini config:

framework = espidf
platform = https://github.com/tasmota/platform-espressif32/releases/download/v2.0.3rc1/platform-espressif32-2.0.3.zip

Note: since framework is IDF, my project includes a copy of Ticker.c/h. Yes I updated them.

Also note: I started a separate project with framework=arduino and was able to implement most needed functionality. The warning message about once_ms() does not occur for the Arduino framework, likely because the libraries are precompiled. The warning message is annoying but at the moment we aren't developing under IDF. I will understand if you want to close out this issue.

[VojtechBartoska]

Thanks for testing, I'm adding this to our Roadmap and we will take a look on it.

[newHeiko]

JFTR: I updated my arduino-esp32 core to 2.0.5 today and this warning now shows up when compiling using the Arduino IDE as well.

Minimalist sketch to reproduce:

#include <Ticker.h>

Ticker tick;

void callbackFunc(int i)
{
  // just a dummy to do something with the parameter
  delay(i);
}

void setup() {
  // put your setup code here, to run once:
  tick.attach(1000, callbackFunc, 30);
}

void loop() {
  // put your main code here, to run repeatedly:
}

Warning message:

In file included from /home/heiko/elektronik/arduino-bugreport/sketch_oct08a/sketch_oct08a.ino:1:
/home/heiko/.arduino15/packages/esp32/hardware/esp32/2.0.5/libraries/Ticker/src/Ticker.h: In instantiation of 'void Ticker::attach(float, void (*)(TArg), TArg) [with TArg = int]':
/home/heiko/elektronik/arduino-bugreport/sketch_oct08a/sketch_oct08a.ino:13:37:   required from here
/home/heiko/.arduino15/packages/esp32/hardware/esp32/2.0.5/libraries/Ticker/src/Ticker.h:58:38: warning: cast between incompatible function types from 'void (*)(int)' to 'Ticker::callback_with_arg_t' {aka 'void (*)(void*)'} [-Wcast-function-type]
     _attach_ms(seconds * 1000, true, reinterpret_cast<callback_with_arg_t>(callback), arg32);
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Compiling for ESP32-S2, compiler warnings: All.

Hope this helps,
Heiko

P.S: With my limited understanding of C++ templates, I guess the issue is the hard "void *" argument of callback_with_arg_t vs. the more flexible TArg.