CODEWITHSUNDEEP
c++floating-point
Popgalop
Popgalop

Reputation: 757

Is a float 4 bytes on all windows platforms

I am writing a program in c++, that stores different data in a binary file. I am running into issues because the size of a data type can change from one system to another. I was wondering if floats are always 4 byte on all windows platforms. The only platform i am building this program for is windows.

Upvotes: 2

Views: 2451

Answers (4)

Carey Gregory
Carey Gregory

Reputation: 6846

Windows does not define the size of float -- your compiler defines that.

What Windows defines is a type named FLOAT in windef.h. It's defined as typedef float FLOAT;. That's the type name the Win32 API uses and the one you should be using if Windows support is important to you. I doubt any Windows compiler will ever change its format for float types, but Microsoft certainly could change their typedef for FLOAT and that would change what it means to support float on all versions of Windows.

Upvotes: 0

Yu Hao
Yu Hao

Reputation: 122383

Not guaranteed by the C++ standard, but most machines today follows ISO/IEC/IEEE 60559:2011, or the identical IEEE-754 floating point standard. By this standard, the single precision float is 4 bytes.

You can check std::numeric_limits< float >::is_iec559 in <limits> to make sure.

Upvotes: 3

Rahul Tripathi
Rahul Tripathi

Reputation: 172428

Yes it has 4 bytes only but it is not guaranteed. You may check the IEEE floating point for reference.

You can check by cross platform behavior like this:-

#include <cassert>
int main () {
    assert(sizeof(float) == 4);
    // If control goes here you can be sure float is 4 bytes.

}

Upvotes: 1

Stack Overflow is garbage
Stack Overflow is garbage

Reputation: 247969

Yes. Of course, it may be wise to throw a static_assert(sizeof(float)==4, "whatever") in there (or a plain old non-static assert, if the former is not supported by your compiler), just to (a) document your assumption, and (b) notify you if by some cruel twist of fate your platform suddenly does not have 4-byte floats.

Upvotes: 2

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