printf format warnings (-Wformat) regarding type definition change from Arduino 2 to Arduino 3 for uint32_t and int32_t

[mathieucarbou]

Platformio:

PLATFORM: Espressif 32 (2024.4.12+sha.9d4b8e6) > Espressif ESP32 Dev Module
HARDWARE: ESP32 240MHz, 320KB RAM, 4MB Flash

platform = espressif32
platform_packages=
  platformio/framework-arduinoespressif32 @ https://github.com/espressif/arduino-esp32.git#3.0.0-rc1
  platformio/framework-arduinoespressif32-libs @ https://github.com/espressif/esp32-arduino-libs.git#idf-release/v5.1
board = esp32dev

Switching to Arduino 3 leads to several printf warnings regarding type definition changed from int to long.

Example:

/Users/mat/Data/Workspace/me/WebSerialLite/examples/demo_ap/demo_ap.ino: In function 'void loop()':
/Users/mat/Data/Workspace/me/WebSerialLite/examples/demo_ap/demo_ap.ino:53:22: warning: format '%u' expects argument of type 'unsigned int', but argument 3 has type 'uint32_t' {aka 'long unsigned int'} [-Wformat=]
   53 |     WebSerial.printf("Free heap=[%u]\n", ESP.getFreeHeap());
      |                      ^~~~~~~~~~~~~~~~~~  ~~~~~~~~~~~~~~~~~
      |                                                         |
      |                                                         uint32_t {aka long unsigned int}

The problem is that printf format is setup by the developer according to the expected type of the argument. If those type change, the format might become incorrect.

In the example above, fixing the format for Arduino 3 would make it wrong for Arduino 2...

What would be the solution for library developer to maintain a compatibility with Arduino 2 & 3 in such case ?

I saw some old issues referencing this same problem but they seemed to be closed or left:

• Esp32c3 int32_t should be int and not long int #5086
• Esp32c3 int32_t should be int and not long int (IDFGH-5124) esp-idf#6906

Other Steps to Reproduce

No response

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

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

[igrr]

Have replied in the linked issue, but just to keep this one answered: the recommended approach for library developers is to use fixed-width format specifier macros from <inttypes.h> when printing uint32_t and int32_t values: PRIu32, PRId32, PRIx32 and so on. This is the most portable approach, these macros should always resolve to the correct specifiers for any given toolchain.

[VojtechBartoska]

Closing this ticket as asnwered, if needed you can reopen. Thank!

[mathieucarbou]

I confirme that using PRIu32 where applicable solved the warnings for me.