Comment by kccqzy

1 day ago

Yeah but fixed width strings don’t need null termination. You know exactly how long the string is. No need to find that null byte.

14 comments

kccqzy

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ninkendo  1 day ago

Until you pass them as a `char *` by accident and it eventually makes its way to some code that does expect null termination.

There’s languages where you can be quite confident your string will never need null termination… but C is not one of them.

  • kccqzy  1 day ago

    You don’t do that by accident. Fixed-width strings are thoroughly outdated and unusual. Your mental model of them is very different from regular C strings.

    • arka2147483647  1 day ago

      Sadly, all the bug trackers are full of bugs relating to char*. So you very much do those by accident. And in C, fixed width strings are not in any way rare or unusual. Go to any c codebase you will find stuff like:

         char buf[12];
   sprintf(buf, "%s%s", this, that); // or
   strcat(buf, ...) // or
   strncpy(buf, ...) // and so on..

      2 replies →

    • ninkendo  1 day ago

      The mental model doesn’t matter, it’s the compiler’s model that is going to bite you. If the compiler doesn’t reject it, it will happen eventually.

Sharlin  1 day ago

Good luck though remembering not to pass one to any function that does expect to find a null terminator.

  • kevin_thibedeau  1 day ago

    Ignore the prefix and always treat strncpy() as a special binary data operation for an era where shaving bytes on storage was important. It's for copying into a struct with array fields or direct to an encoded block of memory. In that context you will never be dependent on the presence of NUL. The only safe usage with strings is to check for NUL on every use or wrap it. At that point you may as well switch to a new function with better semantics.

    • masklinn  15 hours ago

      > an era where shaving bytes on storage was important

      Fixed size strings don’t save bytes on storage tho, when the bank reserves 20 bytes for first name and you’re called Jon that’s 17 bytes doing fuckall.

      What they do is make the entire record fixed size and give every field a fixed relative position so it’s very easy to access items, move record around, reuse allocations (or use static allocation), … cycles is what they save.

      1 reply →

  • integralid  1 day ago

    That's not a problem with strncpy, right? Fixed width records are a thing of the past, and even then it was only used for on-disk storage.

  • andrepd  1 day ago

    Seriously. We have type systems and compilers that help us to not forget these things. It's not the 70s anymore!