Underlying type of character constants and \"plain char

[misra-c]

While C considers plain char, signed char and unsigned char to be integral types, MISRA-C considers plain char to be a distinct underlying type which is used only for \"character\" data.

From your examples,

Code:

unsigned int c = 'x';  /* Not a \"conversion from signed to unsigned\" violation? */

This breaks rule 6.2.

Code:

void foo(int x) {
  unsigned int c = x;  /* Violation: conversion from signed to unsigned. */
}

This breaks 10.1.