10.3 Clarification on assigning unsigned literal to signed

[misra-c]

The result of the cast "(int8_t)256U" is implementation-defined since 256 can not be represented by a signed 8-bit type. A tool supporting directive 1.1 may generate a warning in order to direct the user to document the behaviour of such a cast.

We would recommend removing the "U" rather than adding a cast.

Code:

int8_t s8a = 256;  // implicit narrowing conversion violates rule 10.3

An alternative would be to use a mask so that the value always fits the int8_t range.

Code:

int8_t s8a = (int8_t)(256U & 0xffU);