Modulo operator broken on uint64_t

[Heiko Jakob]

Modulo operator '%' seems to be broken on uint64_t.
The following code crashes the MCU and put's me into the reset handler.
Simply switching uint64_t to uint32_t and it works.

int main(void) {
    int64_t j = 0;
    for (j = 0; j < 10000; j++) {
        if (j % 1000 == 0) {
            __asm__("nop");
        }
    }
}

Compile options:
arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -mfloat-abi=softfp -ffunction-sections -fdata-sections -Os -flto -fno-exceptions -c -g -Ilibopencm3/include -Iinclude -std=c11 -MMD -MP -MF "build/Debug/GNU_ARM_NONE_EABI_5_4-Linux/src/olimexino/main.o.d" -o build/Debug/GNU_ARM_NONE_EABI_5_4-Linux/src/olimexino/main.o src/olimexino/main.c
mkdir -p dist/Debug/GNU_ARM_NONE_EABI_5_4-Linux

Linker options:
arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -mfloat-abi=softfp -ffunction-sections -fdata-sections -Os -flto -fno-exceptions -o dist/Debug/GNU_ARM_NONE_EABI_5_4-Linux/olimexino-stm32-bug build/Debug/GNU_ARM_NONE_EABI_5_4-Linux/src/olimexino/main.o -Llibopencm3/lib -lopencm3_stm32f1 -mthumb -mcpu=cortex-m3 -mfloat-abi=softfp -Tstm32/f1/stm32f103xb.ld -lgcc -nostartfiles -nostdlib -nodefaultlibs -fno-exceptions -ffunction-sections -fdata-sections -Os -flto -Wl,--gc-sections -static

Linker script was used from libopencm3 for stm32f103rbt6 (included in the example code)
I've attached a code example modulo-bug.tar.bz2

Compiler used:
Binary package gcc-arm-none-eabi-5_4-2016q3-20160926-linux.tar.bz2 from launchpad.net
arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 5.4.1 20160919 (release) [ARM/embedded-5-branch revision 240496]

host machine:
$ uname -a
Linux wrkst01 3.16.0-4-amd64 #1 SMP Debian 3.16.36-1+deb8u1 (2016-09-03) x86_64 GNU/Linux
$ cat /etc/debian_version
8.6

target machine:
Olimex Olimexino-STM32 (STM32F103RBT6)

With best Regards
Heiko Jakob

[Andre Vieira (andre-simoesdiasvieira)]

Hi Heiko,

Why are you passing -mfloat-abi=softfp? The Cortex-M3 does not support Floating-Point Extensions.

This combination of options leads to the selection of our default multilib which was build for ARMv4T which supports ARM code and this is why you are getting a ldivmod implementation in ARM mode. Which obviously will not run for a Cortex-M3.

Pass either -mfloat-abi=soft or just leave out the -mfloat-abi option altogether, which defaults to 'soft'.

Best Regards,
Andre

[Heiko Jakob (heiko-jakob)]

On 17.10.2016 12:09, Andre Vieira wrote:
> Hi Heiko,
>
> Why are you passing -mfloat-abi=softfp? The Cortex-M3 does not support
> Floating-Point Extensions.
>
> This combination of options leads to the selection of our default
> multilib which was build for ARMv4T which supports ARM code and this is
> why you are getting a ldivmod implementation in ARM mode. Which
> obviously will not run for a Cortex-M3.
>
> Pass either -mfloat-abi=soft or just leave out the -mfloat-abi option
> altogether, which defaults to 'soft'.
>
> Best Regards,
> Andre
>
> ** Changed in: gcc-arm-embedded
> Status: Confirmed => Invalid
>
Oh ! Thanks !

I didn't know that softfp ain't software emulated floating point.

With best Regards
Heiko Jakob