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The c_str variable is used to traverse the character string containing the command line to be parsed. As characters are retrieved from this pointer, they are stored in a variable of type int. For compilers in which the char type defaults to signed char, this value is sign-extended when assigned to the int variable. For character code 255 decimal (−1 in two's complement form), this sign extension results in the value −1 being assigned to the integer, which is indistinguishable from EOF.

Noncompliant Code Example

This problem was repaired by explicitly declaring the c_str variable as unsigned char.

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static int yy_string_get() {
  register char *c_str;
  register int c;

  c_str = bash_input.location.string;
  c = EOF;

  /* If the string doesn't exist or is empty, EOF found */
  if (c_str && *c_str) {
    /* Cast to unsigned type */
    c = (unsigned char)*c_str++;

    bash_input.location.string = c_str;
  }
  return (c);
}

Noncompliant Code Example

In this noncompliant example, the cast of *s to unsigned int may result in a value in excess of UCHAR_MAX because of integer promotions, consequently causing the function to violate ARR30-C. Do not form or use out of bounds pointers or array subscripts, leading to undefined behavior:

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