Is it safe to use long long data type in a win32 windows OS?

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Is it safe to use long long data type in a win32 windows OS?

I am using sqlite datatabase for a certain app. I noticed that the INTEGER PRIMARY KEY AUTO INCREMENT data type is of data type long long ( but typedefed in sqlite).

I also noticed that the long long data type is 64 bit in size.

Is it really safe and proper to use this data type for an app that is meant for a 32 bit OS?

Posted 11-Dec-14 1:23am

Gbenbam

Updated 11-Dec-14 1:28am

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CPallini 12-Dec-14 7:48am

Yes, of course.

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KarstenK · Answer 1 · 2014-12-11T02:49:00

Solution 1

yes it is shure, but check that the 64-bits are at all times preserved. No casts and no signed / unsigend mismatch.

I would use a own typedef datatype to make it obvious.

typedef MY_KEY_TYPE unsigned __int64

Posted 11-Dec-14 2:49am

KarstenK

W∴ Balboos, *GHB* · Answer 2 · 2014-12-11T08:16:00

In principle, there's no restriction to the datatype size, regardless of the OS, or for that matter, the CPU. When building the program, the compiler handles the way the math is done. If you've a 32-bit cpu, you can still do 64-bit arithmetic. It's just not efficient.

Better put: a cpu is most efficient on the data type for which it is designed: it has registers of the appropriate size and mathematical operations between these registers (more-or-less) directly. A 32 bit system will do, for example, a 64-bit add, but it will take multiple steps (high-order and low order addition and taking care of any "carry over"). When defining data types, INT will be defined as the native size for the targeted O/S. A SHORT is at least 16bit, a LONG, at least 32, etc., but an INT depends . . !

Most current CPU's are 64-bit. A matching OS type means it will run more efficiently (faster).

It is important, however, that you never mix double-long ints with others when doing any operations: if you do, there will be truncation errors and these are irrecoverable once they are applied to your data. Overflows are another possibility. This rule always applies! Not just for double-longs!