For this reason, platform designers were motivated to provide some 32 bit type, which by elimination needs to be int (it can't be char, which must be 8 bits, it can't be short or else you have no 16 bit type, so it must be int or long, but a 16 bit int is silly). Initial 64 bit ABIs were defined with 64 bit int types (ILP64 platforms, such as the first SPARC64 Solaris port) and the problems quickly became apparent when random C software packages failed to configure, compile, or work. Switching to LP64/LLP64 (where int is 32 bits and long is 32 resp. 64 bits) fixed this, at the cost of having to reeducate programmers to use size_t for array indexing. The decision between LP64 and LLP64 was then probably motivated by time_t, which traditionally is a long. If you do LLP64, long and thus time_t is 32 bits and you'll fall prey to the year 2036 problem. Or you use long long for time_t, breaking compatibility with ANSI C and a lot of old software. Most UNIX platforms decided to use LP64 thus, while non-UNIX platforms without this issue frequently went with LLP64 instead, reaping the benefit of staying compatible with software that assumes long is 32 bits.

These days, you probably need only three platform-dependently-sized types (as Go does):

- int/uint for array indexing; native word size, signed and unsigned - uintptr for round-tripping data pointers

uintptr needs to be different as there are a few platforms where pointers are larger than indices, for example:

- on 8086 and i286, pointers are 32 bits (segment+offset) in some code models, while indices are only 16 bits - on IBM iSeries, pointers are 128 bits, while indices are 32 or 64 bits - on capability architectures like CHERI, capabilities (pointers) are 128 bits and need special treatment, while integers are 32 or 64 bits - on MSP430X, pointers are 20 bits (!) while integers are 16 bits

Conceivably one might also need a separate type for text pointers, as these are some times of different size than data pointers (e.g. on PIC), but as arithmetic on text pointers does not generally make sense, a corresponding integer type can perhaps be omitted (use a generic function type). This also helps with platforms like PowerPC, where text pointers are pairs of addresses (entry+toc).

C's ptrdiff_t can be omitted if you follow C semantics, where differences between pointers are only meaningful within the same object, as that's just int. intptr_t does not really make a lot of sense, pointers are unsigned except on weirdo platforms (such as balanced ternary machines).

C's maxalign_t and (u)intmax_t are problematic, as they fail when the architecture is expanded with new features. For example, maxalign_t might have an 8 byte alignment on x86, but then you add SSE which requires a 16 byte alignment, AVX with a 32 byte alignment, AVX-512 with a 64 byte alignment and so on. Not good news. Same for (u)intmax_t, which end up stopping you from ever supporting larger integer types. It is not entirely clear what the solution is. For maxalign_t, perhaps the maximum alignment can be queried at runtime. For (u)intmax_t, perhaps use generic programming to instantiate the relevant code paths for the actual type used.

That said, the key insight of the exception craze is that error returns are a normal part of a functions behaviour and as such should not use extraordinary control flow to take place.

Exceptions (panics) are used for things that should never happen or are indicative of a programmer error, like nil dereferences or out-of-bounds array accesses. That is, things where the programmer is not expected to provide reasonable behaviour on the API level if it happens (but perhaps there is a whole-program fault handler to shut down cleanly).

Opening a file that does not exist? Database record not found? Invalid credentials? These should be anticipated by the programmer and can occur at any time. Not exceptions, normal return values. Go requests that you think about these possibilities instead of pretending they can be ignored.

Silently returning some (the wrong) value is always worse than catching the error right then and their and panicking. A panic is a noticeable symptom of something just having go wrong that is easy to chase after and debug. A silently returned wrong value just causes data corruption down the line, at great pain. It is very annoying to debug, in particular if people start to some times rely on this behaviour as an intentional part of their data flow.

If most of your error handling is just bubbling the error up, you are doing something wrong.

  if err != nil { return err; }

That said, as you seem to actually want to do something with the results, you'll take a branch per match anyway, so I don't see the problem.

Comments URL: https://news.ycombinator.com/item?id=46428496

Points: 222

# Comments: 49

1. Compute M1 = ~A & ~B, which is the mask of all spaces that are not newlines 2. Compute M2 = M1 + (A << 1) + 1, which is the first non-space or newline after each newline and then additional bits behind each such newline. 3. Compute M3 = M2 & ~M1, which removes the junk bits, leaving only the first match in each section

Here is what it looks like:

    10010000 = A
    01100110 = B
    00001001 = M1 = ~A & ~B
    00101010 = M2 = M1 + (A << 1) + 1
    00100010 = M3 = M2 & ~M1

The other stuff is all present in ARMv8.5 I think.