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Comment by marcoms | Hacker News Reader

Why not fixed-size ints - uint8_t, etc. from stdint.h? I've not been using C for a while, so I wonder what the viewpoints are regarding this.

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You typically want to use the native integer size for something like this, for the code to be more portable. The native integer size should really be int, but it's not defined as such in the standard. My preference at the moment:

off_t for file offsets

ptrdiff_t for memory offsets (vs. size_t for unsigned)

int for return flags

A problem with this is that printf does not have sizes to match these.

But then you get different behavior depending on the platform, which doesn't seem any more portable to me.

I'm in the "never use fixed size integers unless needed"-camp. For example, if you write code that's supposed to run on an 8-bit computer (something embedded) as well as your 64-bit desktop, it makes no sense to limit yourself. For example, say that you know that your number will be between 1-200, you could use uint8_t. But why not use int? It will be the native width of the platform, and likely to be faster. Calculations on an 8-bit int can be slower than 64-bit ints on your 64-bit CPU, because the CPU might have to mask out the relevant part of the register to only operate on your 8 bits. And you don't gain anything by writing uint8_t, you still need to occupy a register on your CPU (which will be 64-bit). The behavior of your program will be the same on both platforms.

In practice, how much of my code is going to be run on an 8-bit CPU? Zero. I'd rather have the clarity and consistent behavior of explicitly typed ints than pre-optimize for something that will almost certainly never happen.

The C8051 architecture is still very much a thing in the MCU world. (As is Atmel AVR.)

There were so many bad programmers who assumed 32 bit machines would last forever, that now we're stuck with compilers that don't default to 64 bit ints even building for 64 bit targets.

I don't see how explicit int sizes makes this any worse...

This will bite you if your code depends on int being 32 bit (for example if you depend on overflows or use asm). If your code explicitly uses an int32, this will always be true.

Silently increasing the size of an int is more likely to break things than it'll be helpful. If you really want an int to be 32 bit on a 32 bit machine and 64 bit on a 64 bit machine, make it explicit (e.g. intptr_t for pointers)

In that situation you could use uint_fast8_t which is the fastest uint of at least 8 bits.

I think it has more to do with memory use. See for instance the "65535 interfaces ought to be enough" thread. If you allocate a bazillion of a certain structure, then using the shortest allocation unit for its fields can make a difference, especially if you have a lot of these "small" fields.

I have yet to use a C compiler for an 8-bit platform where int was the native size. sizeof (int) should be at least two chars. Using int instead of an uint8_t where you know its values to fall within those limits would be detrimental to performance in such cases.

That said, the code bases that target both 64- and 8-bit architectures probably aren't that many and both our points are insignificant in those other 99.9% of cases.

The standard requires at least 16 bits in a short and 32 in a long. Oddly "all numeric types are 96 bits" would be fine.

There are whole languages that eschew this approach to portability. Rust is portable, and the language defines u8, u16, u32, u64 to exist, always.

there are also int_least8_t or what ever size and signedness too. or int_fast8_t. You explicitly state I want at least 8 bits or I want at least 8 bits but whatever is fastest.

For ptrdiff_t: "%td"

For size_t: "%zu"

There's no format for off_t, though. The best you can do is to typecast it to intmax_t, and then use "%jd".

Fixed sized integers are useful in two situations (that I can think of); if you're interfacing with a language that doesn't use the same integer size as your C compiler, or if you're relying on integers being a certain width (maybe you're casting between integers and non-integers, or writing a certain number of bytes to a binary file).

I doubt either of these situations come up when dealing with line sizes in a text editor.

And a third situation: Writing device drivers interfacing with hardware registers of specific sizes, although you should use `{u}int_least<N>_t` for that, to give the compiler some leeway with alignment.

There are many cases where using fixed size types can save a significant amount of memory (and your application is constrained by memory on some platform) or CPU time (design to minimize cache misses happens all the time in high performance applications like games).

Neither of these situations is happening in a text editor application though.

Best of both worlds: uint_fast8_t / uint_least8_t gives you at least 256 discrete values and likely a native/optimal-register-width allocation.

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