Function definitions in K&R format (formal parameters of _Bool type)

11.1.5 Function definitions in K&R format (formal parameters of _Bool type)

When the function definition that includes a _Bool-type parameter is written in the K&R format, an assembly code that assigns the argument value to the _Bool-type parameter without change is generated. Therefore, if the _Bool-type
argument has a value other than 0 or 1, a value which is neither 0 nor 1 will be set to the parameter.

Example

void sub();

signed char c;

void func(void) {

        sub(2);

void sub(b)                     // 2 is set to parameter b.

_Bool b;

        if (b == 0 || b == 1) {

                c = b;

        } else {

                c = -1;         // -1 is set to c.

(Workaround)

Write the function definition including a _Bool-type parameter and the function declaration in the function prototype
format.

void sub(_Bool);                // Function prototype

signed char c;

void func(void) {

        sub(2);

void sub(_Bool b)               // Function prototype

        if (b == 0 || b == 1) {

                c = b;

        } else {

                c = -1;