In C, does sizeof measures its result in octet bytes or chars?

Question

Although a char is composed of 1 byte on all compilers I know, I was under the impression that C doesn't guarantee the length of a char, it only guarantees that char < short < long. Therefore I assumed that sizeof measures its result in chars in order to abstract from the platform it's running on. To make it more general, I thought that size_t is defined in terms of char.

But now, as far as I can see searching on google, it appears that sizeof does return its result in bytes.

Was I completely wrong in my assumption or is there more to it than that?

Answer 1

char is the C data type that represents a byte; they're conceptually the same.

If you're asking whether the result is always in octet's (8-bit values), the answer is no; it's in bytes (chars), and if a byte happens to have a different number of bits then the result will be in terms of multiples of that many bits.

Answer 2

The unit used by sizeof is the char. One of the axioms of the language is that sizeof(char) == 1.

Hence, for systems where char is larger than 8 bits, sizeof does not measure in 8 bit units.

Answer 3

The units for sizeof is chars.

However, C defines a byte to be the size of a char, and not the more common usage where a byte equals 8 bits.

If you want to know how many bits a char is, use the CHAR_BIT constant in <limits.h>