sizeof int?

This is a discussion on sizeof int? within the Tech Board forums, part of the Community Boards category; I have a quick question: I just got a 64bit cpu(finally) and want to port my apps over to 64bit, ...

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    sizeof int?

    I have a quick question: I just got a 64bit cpu(finally) and want to port my apps over to 64bit, I start up a test project and set it to x64; I code in some vars and one is set to sizeof(int). I get a 4 as the size of int, It was my assumption that int is 8 bytes on x64 and 4 on 32bit. is this the expected behavior, or is something amiss? I'd rather not have to start using __int64 for 64bit vars.


    I also have another question, you know how if you used __int64 on a 32bit project it would in assembler use the slow version of 64bit addition, is there any equivilant __int128 ?


    I'm using Microsoft Windows 7 (x64), Microsoft Visual Studio 2008 Team System

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    Jack of many languages Dino's Avatar
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    I suspect you'll have to use a long, not int, if you want 8 byte integers.
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    I think on Linux with gcc amd64 an int is 4 bytes as well. Though a long is 8 bytes, where it is 4 bytes on x86.

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    spurious conceit MK27's Avatar
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    Yeah I recall being slightly confused by this as well.

    It's actually the pointers that have doubled in size -- on 32-bit they are 4 bytes, but a 64-bit pointer is 8 bytes.
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    Maybe this will help.
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    C++まいる!Cをこわせ! Elysia's Avatar
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    I would suggest using size types if you want a variable to be of a specific size. They are available in C99 (the stdint.h header can be downloaded from Wikipedia, just look at the stdint.h entry), and also in Boost (called cstdint and lives in the boost namespace [C++ only]).
    The size of variables change depending on whether it's x64 or x86 and platform (OS), as well as compiler.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    int "should" be 64-bit in 64-bit mode, since all the general purpose registers are 64-bit, but for practical reasons (compatibility), on x86-64, it's still 32-bit.

    To get 64-bit everywhere, you can use "long long". To get 32-bit everywhere, use int. long is 32-bit on 32-bit, and 64-bit on 64-bit (like what int should be).

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    C++まいる!Cをこわせ! Elysia's Avatar
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    Define "should". Why "should" int be 64 bits?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    http://www.open-std.org/JTC1/SC22/WG...docs/n1256.pdf

    Page 45.
    5 An object declared as type signed char occupies the same amount of storage as a
    ‘‘plain’’ char object. A ‘‘plain’’ int object has the natural size suggested by the
    architecture of the execution environment (large enough to contain any value in the range
    INT_MIN to INT_MAX as defined in the header <limits.h>).
    x86-64 has 64-bit GP registers and 64-bit pointers. What's a more "natural" size than 64-bit?

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    Malum in se abachler's Avatar
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    according to the standard, at least the last version i read, int is the size of the processors native integer type, which means technically on an x64 it should be a 64 bit integer, however, to not break existing code, most implementations retain int as a 32 bit integer and use long long or __int64 etc. for 64 bit integers.
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    Super Moderator VirtualAce's Avatar
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    For those of us that use MSVS and aren't concerned about the code compiling in another compiler we can just use the signed/unsigned int64 data type provided by the compiler.

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    and the hat of wrongness Salem's Avatar
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    Quote Originally Posted by previous quote
    5 An object declared as type signed char occupies the same amount of storage as a
    ‘‘plain’’ char object. A ‘‘plain’’ int object has the natural size suggested by the
    architecture of the execution environment (large enough to contain any value in the range
    INT_MIN to INT_MAX as defined in the header <limits.h>).
    Not mandatory, suggested.
    And since 32-bits is enough to hold the required INT_MIN to INT_MAX then all is well.

    A hell of a lot of code will implicitly depend on int being 32 bits, and changing the compiler would just break a load of things. Such major changes do not happen between patch levels of a compiler.

    Sooner or later (as it was when 16 bits moved to 32 bits), there will be compilers which have 64 bit integers "out of the box".
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    C++まいる!Cをこわせ! Elysia's Avatar
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    All I see is suggested, not why it should be 64-bit. To the processor, I think it hardly matters.
    And that's an interesting page right there. It claims some interesting stuff, yet that contradicts what everyone has mentioned so far.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Ah, so you are saying int shouldn't be 32-bit on x86-32 as well?

    We can equally well have 16-bit ints on x86-32, but does that make sense?

    Not mandatory, suggested.
    I think there is a subtle difference in our interpretation of the word "suggested" in this context.

    Note that the sentence didn't read
    A ‘‘plain’’ int object is suggested to have the natural size suggested by the
    architecture of the execution environment
    But instead
    A ‘‘plain’’ int object has the natural size suggested by the
    architecture of the execution environment
    So what you are saying is that the intrinsic features of the x86-64 architecture suggests a natural size of 32-bit? What size does x86-32 suggest, then?

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    C++まいる!Cをこわせ! Elysia's Avatar
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    I don't really refer to the standard, either. Why should it be the 64 bits or 32 bits? Why, really, does it matter?
    Int could as well have been 16 bits on x86, yes, but it wasn't. No shame in that.

    Regardless, it's dangerous to rely on things being specific sizes. That's why we have common typedefs that allows us to create a variable of precise size.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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