[BUG] Increment and decrement of volatile is deprecated

[mathiasgredal]

When using FreeRTOS on RP2040 and with C++20 and Pico-SDK, you get a warning that volatile increment and decrement is deprecated:

In function 'void vPortRecursiveLock(BaseType_t, uint32_t, spin_lock_t*, BaseType_t)':
portable/ThirdParty/GCC/RP2040/include/portmacro.h:230:51: warning: '++' expression of 'volatile'-qualified type is deprecated [-Wvolatile]
  230 |                 ucRecursionCountByLock[ ulLockNum ]++;
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
portable/ThirdParty/GCC/RP2040/include/portmacro.h:244:50: warning: '--' expression of 'volatile'-qualified type is deprecated [-Wvolatile]
  244 |         if( !--ucRecursionCountByLock[ ulLockNum ] )
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^

[ActoryOu]

Hi @mathiasgredal,
Thanks for bringing this to us! Would you like to create PR to fix this warning?

Thank you.

[htibosch]

Hi @mathiasgredal, thanks for reporting this. Have you compiled and tried the Raspberry project? Did you ever see asserts from this function?

Mentioned code would deserve this warning, unless spin_try_lock_unsafe() is taken into account: it makes sure that the fetch/increment/store will happen in an atomic manner.

But still, MISRA wouldn't like this code:

    if( !--ucRecursionCountByLock[ ulLockNum ] )
    {
    }

because it is confusing.

Maybe this would be accepted:

    uint8_t uc = ucRecursionCountByLock[ ulLockNum ] - 1;
    ucRecursionCountByLock[ ulLockNum ] = uc;
    if( uc == 0U )
    {
    }