C++ sizeof integral types

I have heard from books, presentation about minimal size for integral types in C/C++

Sizes below are in bytes:

• sizeof(char) >= 1
• sizeof(short) >= 2
• sizeof(long) >= 4
• sizeof(long long) >= 8

But I cannot find those guarantees in standards. So are there any guarantees required by compilers to implement defined in standards C++98 / C++2003 / C89 / C99?

Because there are none. Standard defines only some basic guarantees and requirements regarding values. You can find them in this document on page 33:

5.2.4.2.1 Sizes of integer types .

You can be sure, that:

sizeof(char) ≤ sizeof(short) ≤ sizeof(int) ≤ sizeof(long) ≤ sizeof(long long)

and

sizeof(float) ≤ sizeof(double) ≤ sizeof(long double)

Also:

• sizeof(char) is guaranteed to be 1
• sizeof(char) == sizeof(signed char) == sizeof(unsigned char)

Also, on most platforms:

• sizeof(char) = 1
• sizeof(short) = 2
• sizeof(int) = 4
• sizeof(long) = 4
• sizeof(long long) = 8 (1)

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(1) long long is not a standard type. GCC and VC++ have supported it for a long time now, but official support came with C++ 11:

C++: Fundamental Types

long long - target type will have width of at least 64 bits. (since C++11)

Note, that even if sizeof(char) is guaranteed to be 1, it doesn't mean, that char is 8 bit long. CHAR_BIT defines number of bits in char type. These days, almost all architectures use 8 bits per byte, but some older architectures used to have 7.