(Command-line option to suppress warning = -w-big) 

Under older versions of C, a hexadecimal escape sequence could contain no more than three digits. 

The ANSI standard allows any number of digits to appear as long as the value fits in a byte. 

This warning results when you have a long hexadecimal escape sequence with many leading zero digits (such as \x00045). 

Older versions of C would interpret such a string differently.