• A (very) limited version of snprintf.
• async-signal-safe
• code based on mysql my_safe_snprintf

/**
  A (very) limited version of snprintf.
  @param   to   Destination buffer.
  @param   n    Size of destination buffer.
  @param   fmt  printf() style format string.
  @returns Number of bytes written, including terminating '\0'
  Supports 'd' 'i' 'u' 'x' 'p' 's' conversion.
  Supports 'l' and 'll' modifiers for integral types.
  Does not support any width/precision.
  Implemented with simplicity, and async-signal-safety in mind.
*/
size_t safe_snprintf(char *to, size_t n, const char *fmt, ...);