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by dev-ns8 81 days ago
Besides my DA/Algo classes in College, I've never used C seriously. And you know, it's semantics like this that really make me go WTF lol....

From strtok man page... "The first time that strtok() is called, str should be specified; subsequent calls, wishing to obtain further tokens from the same string, should pass a null pointer instead."

Really?? a null pointer.. This is valid code:

  char str[] = "C is fucking weird, ok? I said it, sue me.";
  char *result = strtok(str, ",");
  char *res = strtok(NULL, ",");
Why is that ok?
2 comments
kelnos 81 days ago
You have to understand the context, and the time period. Memory and CPU cycles were precious. All computers being 24/7 networked wasn't a thing, so security wasn't much of a concern. API design tended to reflect that.
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dev-ns8 81 days ago
Not mentioned in my initial comment, but yeah, I'm viscerally aware of the affect the time period and resources at the time have on API design in C and other languages from that time period.

The null pointer in place of the operand here just seemed like a really good quirk to point out

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tialaramex 81 days ago
It's like this because the 1970s C programmer, typically a single individual, is expected to maintain absolute knowledge of the full context of everything at all times. So these functions (the old non-re-entrant C functions) just assume you - that solo programmer - will definitely know which string you're currently tokenising and would never have say, a sub-routine which also needs to tokenize strings.

All of this is designed before C11, which means that hilariously it's actually always Undefined Behaviour to write multi-threaded code in C. There's no memory ordering rules yet in the language, and if you write a data race (how could you not in multi-threaded code) then the Sequentially Consistent if Data Race Free proof, SC/DRF does not apply and in C all bets are off if you lose Sequential Consistency† So in this world that's enough, absolute mastery and a single individual keeping track of everything. Does it work? Not very well but hey, it was cheap.

† This is common and you should assume you're fucked in any concurrent language which doesn't say otherwise. In safe Rust you can't write a data race so you're always SC, in Java losing SC is actually guaranteed safe (you probably no longer understand your program, but it does have a meaning and you could reason about it) but in many languages which say nothing it's game over because it was game over in C and they can't do better.

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