Compiling lexical_cast to an integer from a char with gcc and -O3 results in "array subscript -1 is outside array bounds" warnings

[a-kryuk]

Starting with boost 1.85, when compiling the following code (Godbolt)

#include <boost/lexical_cast.hpp>
int f(char n) {
  return boost::lexical_cast<int>(n);
}

gcc -O3 -Wall -Wextra -pedantic produces scary-looking warnings array subscript -1 is outside array bounds.