STDC VERSION

/* * Using C99, assume we have stdint and stdbool */
 * 1) if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
 * 2)  define HAVE_STDINT_H
 * 3)  define HAVE_STDBOOL_H
 * 4) endif

Value
199901L

Found in
h-basic.h