What is the difference between u_int32_t and uint32_t?
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1The latter is defined in C99's header, `stdint.h`. The former is not. From http://lists.freedesktop.org/archives/release-wranglers/2004-August/000925.html it looks like maybe the u_ forms were used in BSD Unix? Anyway, you should use `uint32_t` in your code. – Conrad Meyer Feb 23 '11 at 12:13
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@Conrad Why is this a comment and not an answer? – Core Xii Feb 23 '11 at 12:18
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@Core Xii: *Shrug*. I had never heard of u_int32_t before responding, I'm not an authoritative source on this. – Conrad Meyer Feb 23 '11 at 12:23
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uint32_t is a standard C99 type u_int32_t is used internally in some POSIX implementations.
Šimon Tóth
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[What is POSIX?](https://stackoverflow.com/q/1780599/2023530) This link answers the question which occurred to me. – Hoseyn Heydari Jul 08 '18 at 16:26
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As others have mentioned, uint32_t is a standard C99 type.
Anyway, the takeaway is that if you're writing portable C code or C header files meant to be shared between different devices/architectures, you can use stdint.h.
larryang
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uint32_t is standard C99, while u_int32_t is used on certain Unix platforms.
Unsigned
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The variable type uint32_t is an unsigned 32-bit integer data type defined according to the so-called C99 standard. Not all compilers comply with the standard. And u_int32_t is used for some internally implementations.
metastack
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