isspace-ub.cpp

// show that c99 isspace returns the same result for char and unsigned char
#include <algorithm>
#include <cctype>
#include <climits>
#include <iostream>

int main() {
  for (char c = CHAR_MIN; ; ++c) { // iterate over all char values
    unsigned char u = c;
    if (::isspace(c) != ::isspace(u)) { // error
      std::cerr << static_cast<int>(c) << std::endl;
      return 1;
    }
    if (c == CHAR_MAX)
      break;
  }
}