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Comment by 1718627440

2 days ago

> It balkanizes the language.

Not really, as C has had even more diverse implementations per-standardization. I would say the situation is now, much less diverse under the rule of GCC and Clang. (Yeah MSVC also exists.)

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1718627440

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WalterBright  2 days ago

Every switch that changes the language semantics creates a separate language. If you have n such switches, your compiler is supporting n x n languages. I've also had troubles writing portable C code with all warnings enabled as different compilers contradicted each other on what was acceptable.

I tried pretty hard to make D a warning-less language, but still some crept in grump grump.

Have fun with this one:

    for (int i = 0; i < end; ++i);
        foo(i);

One of the best programmers I know came up to me with this loop and told me my C compiler was broken because the loop was only executed once. I pointed at the ; and you can guess the rest.

I added a warning for that in the C compiler, and for D simply disallowed it. I've noticed that some C compilers have since added a warning for that as well. The C folks should just make it illegal.

I've also fixed printf in D so that:

    char* p;
    printf("%d\n", p);

gives an error message, and the right format to use for `p`. It was a little thing, but it sure found a lot of incorrect formats in my code.

  • 1718627440  2 days ago

    > The C folks should just make it illegal.

    I often have code, which looks like this:

        for (ptr = start; random_condition (*ptr); ptr = ptr->next);
    for (ptr = ptr->next; other_condition (*ptr); ptr = ptr->prev);

    ...  [do action]

    for (ptr = end; to_be_deleted (*ptr) && (delete (ptr), TRUE); ptr = ptr->prev);

    I wouldn't be happy about your policy.

    > I've also fixed printf in D so that [...] gives an error message

    Just last week I had the case that the C compiler complained, I should use %lld for long long, but the printf implementation shipped with the compiler doesn't support that. Thus, using %ld, even if undefined behaviour was the correct action. I wouldn't like my language making up more work for me for no reason.

    • WalterBright  2 days ago

      Rewrite as:

          for (ptr = start; random_condition (*ptr); ptr = ptr->next) { }

      Then anyone reading your code will know the empty loop was intentional. BTW, many C compilers warn about the ; on a for loop.

      Have you ever discovered this bug:

          if (condition);
        doThis();

      It's a hard one to see in a code review. Yes, that's also disallowed in D.

      > I should use %lld for long long, but the printf implementation shipped with the compiler doesn't support that.

      Weird that your compiler would support long long, but with a broken Standard library. I don't see that as a feature. You can always cast the argument to long, and at least you won't get undefined behavior.

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