cortext m0 PRIu8 expands to hhu and is not usable

Bug #1836698 reported by Phil Bolduc on 2019-07-16
This bug affects 1 person
Affects Status Importance Assigned to Milestone
GNU Arm Embedded Toolchain

Bug Description

Package: toolchain-gccarmnoneeabi - gcc-arm-embedded
Version: 1.70201.0
Toolchain: binary package provided with Platform IO in VS Code
Host Machine: Windows 10 x64
Symptom: when using PRIu8 from toolchain-gccarmnoneeabi/arm-none-eabi/include/inttypes.h it expands to hhu on Cortex M0+ processors. This macro is used to format types in printf style functions. On Cortext M0, an integer value is not correctly formatted.

I am using Platform IO inside VS Code on Windows 10. I am compiling a library, MySensors, that uses the PRIu8 macro to format various values. I am using a Moteino M0. I have also checked compiled output for a adafruit feather m0. On these Cortex M0+ processors, the PRIu8 expands to hhu.

When I got to the definition, the the following path using Platform IO's "Got yo Definition"


  #define __PRI8(x) __INT8 __STRINGIFY(x)
  #define PRIu8 __PRI8(u)

The macro expands using the __INT8 macro defined in toolchain-gccarmnoneeabi\arm-none-eabi\include\sys\_intsup.h

#if (__INT8_TYPE__ == 0)
#define __INT8 "hh"
#elif (__INT8_TYPE__ == 1 || __INT8_TYPE__ == 3)
#define __INT8 "h"
#elif (__INT8_TYPE__ == 2)
#define __INT8
#elif (__INT8_TYPE__ == 4 || __INT8_TYPE__ == 6)
#define __INT8 "l"
#elif (__INT8_TYPE__ == 8 || __INT8_TYPE__ == 10)
#define __INT8 "ll"

These are common predefined macros as stated here I am not not really sure where to point the finger on the cause.

Platform IO defines is the SAMD boards here

Is there a compiler flag that Platform IO should be using? I just not sure if it is a Platform IO bug or the toolchain-gccarmnoneeabi - gcc-arm-embedded bug.

Example Program:

#include <Arduino.h>

#ifdef MOTEINO_M0
#define Serial SerialUSB

void setup() {
  while (!Serial);

  char buffer[512];
  uint8_t value = 123;
  snprintf(buffer, sizeof(buffer), "value=%" PRIu8 "\n", value);



void loop() {

// end of example

- platformio.ini

platform = atmelsam
board = moteino_zero
framework = arduino



Expected Output:

Phil Bolduc (pbolduc) wrote :

When adding build_flag = -E, the setup function in generated main.cpp.o file looks like this

void setup() {
  while (!SerialUSB);

  char buffer[512];
  uint8_t value = 123;
  snprintf(buffer, sizeof(buffer), "value=%"
# 18 "src\\main.cpp" 3 4
# 18 "src\\main.cpp"
                                            "u" "\n", value);


# 23 "src\\main.cpp" 3 4
# 23 "src\\main.cpp"

What is your full compile command? Are you using newlib_nano by any chance?

Phil Bolduc (pbolduc) wrote :

Here is the first part of the build log with the arm-none-eabi-g++ command. I have attached the full log.

> Executing task: C:\Users\phil\.platformio\penv\Scripts\platformio.exe run --verbose --environment adafruit_feather_m0 <

Processing adafruit_feather_m0 (platform: atmelsam; board: adafruit_feather_m0; framework: arduino)
PLATFORM: Atmel SAM 3.8.0 > Adafruit Feather M0
HARDWARE: SAMD21G18A 48MHz, 32KB RAM, 256KB Flash
DEBUG: Current (atmel-ice) External (atmel-ice, blackmagic, jlink)
PACKAGES: toolchain-gccarmnoneeabi 1.70201.0 (7.2.1), framework-arduinosam 4.3.190711
LDF: Library Dependency Finder ->
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 20 compatible libraries
Scanning dependencies...
No dependencies
arm-none-eabi-g++ -o .pio\build\adafruit_feather_m0\src\main.cpp.o -c -fno-rtti -fno-exceptions -std=gnu++11 -fno-threadsafe-statics -Os -ffunction-sections -fdata-sections -Wall -mthumb -nostdlib --param max-inline-insns-single=500 -mcpu=cortex-m0plus -DPLATFORMIO=40000 -DARDUINO_ARCH_SAMD -DARDUINO_SAMD_ZERO -DARDUINO_SAMD_FEATHER_M0 -DARM_MATH_CM0PLUS -D__SAMD21G18A__ -DF_CPU=48000000L -DUSBCON -DUSE_TINYUSB -DARDUINO=10805 -DUSB_VID=0x239A -DUSB_PID=0x800B "-DUSB_PRODUCT=\"Adafruit Feather M0\"" -DUSB_MANUFACTURER=\"Adafruit\" -Iinclude -Isrc -IC:\users\phil\.platformio\packages\framework-arduinosam\cores\adafruit -IC:\users\phil\.platformio\packages\framework-arduinosam\system\samd\CMSIS\CMSIS\Include -IC:\users\phil\.platformio\packages\framework-arduinosam\system\samd\CMSIS-Atmel\CMSIS\Device\ATMEL -IC:\users\phil\.platformio\packages\framework-arduinosam\cores\adafruit\Adafruit_TinyUSB_Core -IC:\users\phil\.platformio\packages\framework-arduinosam\cores\adafruit\Adafruit_TinyUSB_Core\tinyusb\src -IC:\users\phil\.platformio\packages\framework-arduinosam\variants\feather_m0 src\main.cpp

Phil Bolduc (pbolduc) wrote :

I have created a corresponding issue on the platform io atmelsam repository,

Phil Bolduc (pbolduc) wrote :

I ran the same sketch with Arduino IDE 1.8.9 and I got the same output,


Where would the problem be? board definition? is there a compiler option to force newlib_nano? How can I check if it is using newlib_nano?

I have attached the build log from Arduino IDE 1.8.9

john (jkovach) wrote :

Must be newlib_nano. I had a similar problem:
The library is selected at link stage. Look for linker command line.

john (jkovach) wrote :

By the way, the full newlib would pull a lot of code. I think it would be wise to accept the limitations of newlib_nano and modify your code like the following:
uint8_t value = 123;
snprintf(buffer, sizeof(buffer), "value=%d\n", (int)value);

Phil Bolduc (pbolduc) wrote :

Thank you for your feedback. This does provide the answer to the original issue. I have submitted a issue on the original library's repository. Since the issue is caused in the linking stage, it could be difficult to at compilation time detect. I would have to know it is the gcc arm embedded toolchain and if running on a micro-controller.

Anyways, I appreciate the feed back and pointing me in the right direction. I think this issue can be closed.

Changed in gcc-arm-embedded:
status: New → Invalid
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