Good introduction to <inttypes.h>

Question

I want to recommend the use of <inttypes.h> to someone doing printf with mixed 32/64 bit builds. I tried to Google an introduction or tutorial page with a few examples and usage guidelines, but I couldn't find one.

Can someone recommend an introduction or tutorial for <inttypes.h>?

Answer 1

Try http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/inttypes.h.html for a start.

A better example of how to use the new portable formatting macros was found in avr-libc. I've included an example (from the link) to illustrate. QNX libraries also have a better human-readable description (if you don't like reading the specification cold), although you have to scroll nearly to the end of the page to get to the meat of the descriptions.

#include <inttypes.h>

uint8_t smallval;
int32_t longval;
...
printf("The hexadecimal value of smallval is %" PRIx8
       ", the decimal value of longval is %" PRId32 ".\n",
       smallval, longval);

Note that this uses the "String" "String" implied concatenation operator to yield the string (in this example)

"The hexadecimal value of smallval is %x, the decimal value of longval is %ld.\n"

An attempt to decompose the naming convention seems to indicate:

• (first three letters)
  • PRI for printf format
  • SCN for scanf format
• (fourth letter)
  • x for hexadecimal formatting
  • u for unsigned formatting
  • o for octal formatting
  • i for integer formatting
  • d for decimal formatting
• (extra letters)
  • 8 for eight bit
  • 16 for sixteen bit
  • 32 for thirty-two bit
  • 64 for sixty-four bit
  • FAST8 for "fast" eight bit
  • FAST16 for "fast" sixteen bit
  • FAST32 for "fast" thirty-two bit
  • FAST64 for "fast" sixty-four bit
  • LEAST8 for "least" eight bit
  • LEAST16 for "least" sixteen bit
  • LEAST32 for "least" thirty-two bit
  • LEAST64 for "least" sixty-four bit
  • PTR for pointer
  • MAX for maximum supported bit size

so PRIx8 means printf format instruction to format to hexadecimal eight bits.