Can I assume the size of long int is always 4 bytes?

Question

Is it always true that long int (which as far as I understand is a synonym for long) is 4 bytes?

Can I rely on that? If no

Answer 1

Short answer: No! You cannot make fixed assumptions on the size of long int. Because, the standard (C standard or POSIX) does not document the size of long int (as repeatedly emphasized). Just to provide a counter example to your belief, most of the 64 bit systems have long of size 64! To maximize portability use sizeof appropriately.

Use sizeof(long int) to check the size, it returns the size of long in bytes. The value is system or environment dependent; meaning, the compiler determines the size based on the hardware and OS.