MISRA C:2023 Rule 1.5

Declaring an identifier with internal linkage at file scope without the static storage class specifier.

The rule checker reports a violation if an identifier is declared multiple times, and some of the declarations have the static storage class specifier while others do not.

The rule checker reports violations on declarations that place a storage class specifier such as static, extern, auto, register or __thread at a position other than the beginning, for instance, after the data type as follows:

int static var; //Noncompliant

Use of function declarators with empty parentheses (not prototype-format parameter type declarators).

The rule checker reports a violation if a function declaration uses empty parenthesis () instead of (void) to indicate no parameters.

Use of function definitions with separate parameter identifier and declaration lists (not prototype-format parameter type and identifier declarators).

The rule checker flags K&R style function definitions where the parameter types are separated from the parameter names like this:

int foo (x, y) //Noncompliant
    int x;
    char y;
{
}

Use of macro ATOMIC_VAR_INIT (defined in stdatomic.h).

The rule checker reports violations on uses of the macro ATOMIC_VAR_INIT (provided there is a previous inclusion of the header stdatomic.h).

Ability to undefine and perhaps then redefine the macros bool, true, and false (defined in stdbool.h).

The rule checker reports violations on #undef and #define statements that undefine and redefine the macros bool, true, and false (provided there is a previous inclusion of the header stdbool.h).

Use of gets() function (defined in stdio.h).

The rule checker reports violations on use of the gets() function (provided there is a previous inclusion of the header stdio.h).

Use of ungetc() function on a binary stream where the file position indicator is zero.

The rule checker reports violations if the function ungetc() is used on a stream where the file position indicator is zero. For instance:

void addToFile() {
    FILE* my_file = fopen("my_file", "a");
    char c;
    c = getc(my_file);
    fseek(my_file, 0, SEEK_SET);
    // File position indicator is 0.
    ungetc(c, my_file); //Noncompliant
}

Use of realloc() function (defined in stdlib.h) with a size argument equal to zero.

The rule checker reports violations on use of the realloc() function with a size argument of zero (provided there is a previous inclusion of the header stdlib.h).