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Comment by 1718627440

4 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.

4 comments

1718627440

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WalterBright  3 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.

  • 1718627440  3 days ago

    > Rewrite as:

    Could do that I just don't like the look. :-)

    > Have you ever discovered this bug:

    Actually no, because the coding style I use either puts it on a single line or with braces. I never indent just a single line.

    So:

        if (condition) doThis ();

    or:

        if (condition)
    {
        doThis ();
    }

    > Weird that your compiler would support long long, but with a broken Standard library.

    Yeah, for your information it was GCC combined with newlib for arm-none-eabi shipped with Debian/MS Windows.