For an explanation of __is_constant(), see the thread where it was suggested: https://lkml.org/lkml/2018/3/20/845 https://lkml.org/lkml/2018/3/20/845 (this was

For an explanation of __is_constant(), see the thread where it was suggested: https://lkml.org/lkml/2018/3/20/845 https://lkml.org/lkml/2018/3/20/845 (this was also indirectly linked to in the article) tl;dr: If one of the expressions in a ternary operator is a null pointer constant, the result type is that of the other expression.