Is it dangerous to promote types in printf arguments?

Question

My questions stem from trying to use printf to log things when trying to build for multiple bit-depth platforms (32/64 for example).

A problem that keeps rearing its ugl

Answer 1

bools/_Bools, chars and shorts are first converted into int (if this conversion preserves the value, else into unsigned int) when passed to variadic functions like printf(). Similarly floats get converted into doubles.

So, if you pass something smaller than int, printf() will grab the whole (unsigned) int without any problems (other than if the passed value is actually an unsigned int and you're printing it with %d instead of %u, you get undefined behavior).

Other types, AFAIR, do not undergo such conversions.

This line:

print (" my int: %ld\n", (long)myInt);

isn't buying you anything over this line:

printf(" my int: %d\n", myInt);

Both are valid and the result will be practically identical. The only difference is that the former might result in bigger code and longer execution time (if sizeof(long) >= sizeof(int)).