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    • STM32429I_Discovery board with printf float support problem

    Posted by David Regan on 2019-08-10 12:43

    Used cube to generate a project with default settings for STM32F429I disco board plus CMSIS V2 rtos and USART 2 half duplex transmit only .

    Code
    float fVal = 345.678;
    printf("Hello World\r\n");
    printf("fVal %f\r\n",fVal);

    Output
    Hello World
    fVal . !

    Issues
    With -specs = nosys.specs -specs= nano.specs -u _printf_float printf causes a hard fault.
    With specs = nosys.specs -specs -u _1st printf OK 2nd printf produces incorrect output

    Project attached

    Reads: 8075
    Posted by johannes.visser@msc-technologies.eu on 2019-12-05 16:08

    Do you use RTOS? I have had the same effect. -u _printf_float seems only to work without RTOS.
    The effect seems to be a faulty malloc heap overflow check in syscall.c
    printf("%f") uses malloc. With RTOS, malloc does not return any memory and printf continues with a null pointer.
    See this topic https://www.openstm32.org/forumthread353