[Bug] Undefined behavior in LL_ADC_SetChannelSingleDiff causes it to alway set bits in gcc and clang

[Morty Morty]

From LL_ADC_SetChannelSingleDiff:

 /* Bits of channels in single or differential mode are set only for        */

 /* differential mode (for single mode, mask of bits allowed to be set is   */

 /* shifted out of range of bits of channels in single or differential mode. */

The assumption that it is ok to shift the bits out of the register is wrong, because it is undefined bahviour: C11 6.5.7 / http://c0x.coding-guidelines.com/6.5.7.html

This causes gcc (https://godbolt.org/z/eH-T_m), as well as clang (and therefore probably armcc, too), to replace the bic-instruction with an orr-instruction; inverting the intent.

The reasoning why they do that can be found here:

https://gcc.gnu.org/ml/gcc/2019-03/msg00077.html

[Imen.D]

Hello Morty,

Thanks for reports this issue.

We will look on this issue, then we will keep you updated.

Kind Regards,

Imen

[Imen.D]

Hello @Moritz Strübe​ ,

This issue will be fixed on the coming release of all relevant STM32 series.

Thank you for your contribution.

Best Regards,

Imen