27

I was wondering what is the difference between uint32_t and uint32, and when I looked in the header files it had this:

types.h:

    /** @brief 32-bit unsigned integer. */
    typedef unsigned int uint32;
stdint.h:

    typedef unsigned   uint32_t;

This only leads to more questions: What is the difference between

unsigned varName;

and

unsigned int varName;

?

I am using MinGW.

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3
  • 9
    They're the same. However the type uint32 (and the header <types.h> or the file "types.h") is not defined by the C99 Standard. If you want to use one of those types, use uint32_t and include the header <stdint.h>. Also unsigned and unsigned int are the same. Commented Aug 2, 2012 at 21:34
  • 1
    So uint32 and <types.h> are not part of the standard, but uint32_t is? Commented Aug 2, 2012 at 21:40
  • 2
    @user1507133: Yes. Basically, there's no such thing as uint32 neither in C nor in C++. Commented Aug 2, 2012 at 21:42

4 Answers 4

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23

unsigned and unsigned int are synonymous, much like unsigned short [int] and unsigned long [int].

uint32_t is a type that's (optionally) defined by the C standard. uint32 is just a name you made up, although it happens to be defined as the same thing.

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1 Comment

A bit of necromancy here, but comparing unsigned [int] to [unsigned] (short|long) [int] may give new programmers the false impression that short and long are unsigned by default. I'd suggest unsigned (short|long) [int] instead.
6

There is no difference.

unsigned int = uint32 = uint32_t = unsigned in your case and unsigned int = unsigned always

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3 Comments

unsigned int == unsigned, but it is not in any way guaranteed that uint32_t == unsigned int. unsigned int can have any bit-width from 16 bit and up.
In an environment with those particular typedefs, uint32_t is by definition unsigned int.
@AndreyT: that's why I wrote "in your case"
4

unsigned and unsigned int are synonymous for historical reasons; they both mean "unsigned integer of the most natural size for the CPU architecture/platform", which is often (but by no means always) 32 bits on modern platforms.

<stdint.h> is a standard header in C99 that is supposed to give type definitions for integers of particular sizes, with the uint32_t naming convention.

The <types.h> that you're looking at appears to be non-standard and presumably belongs to some framework your project is using. Its uint32 typedef is compatible with uint32_t. Whether you should use one or the other in your code is a question for your manager.

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4 Comments

"<stdint.h> is a standard header in C99". What about C++98 and C++11?
<cstdint> is, I think, the equivalent C++ standard header.
@user1507133 - C++11 has <cstdint> which brings these types into the std namespace (e.g. std::uint32_t). C++98 does not have this header because it predates C99. POSIX provides inttypes.h with the same types if that is good enough.
According to the C Standard, <inttypes.h> includes <stdint.h>. So it "copies" every definition and provides a few extra ones (notably scanf and printf specifiers: printf("%" PRIu32 "\n", x);
2

There is absolutely no difference between unsigned and unsigned int.

Whether that type is a good match for uint32_t is implementation-dependant though; an int could be "shorter" than 32 bits.

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