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Mildly interesting quirks of C

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Re: Mildly interesting quirks of C

#4

Post by veltas »

"Flat Initializer Lists" is given as an example in K&R C I think, at least the first edition, when writing those extra braces to fill out an initializer must have felt very redundant.

These days many compilers will warn if you do this, however, as it is rare people do this and usually indicates a misunderstanding of the type used.

I think it's quite readable though, so it's a shame it causes warnings. What do you think?

  struct { const char *name; int age; } records[] = {
      "John",   20,
      "Bertha", 40,
      "Andrew", 30,
  };

Re: Mildly interesting quirks of C

#5

Post by veltas »

xcdzvyn wrote: post #3

While a few of these were interesting I'd love to see a short technical explanation of each quirk for the feeble high-level programmer (me). The first one for example, is foo initialised? How so?

I think it's aimed at C programmers. foo is a struct, so it's a type, it's not a variable. The point is just that struct bar is also defined by the definition of struct foo.

Re: Mildly interesting quirks of C

#8

Post by hoosieree » 

    8. Modifiers to array sizes in parameter definitions [https://godbolt.org/z/FnwYUs]
    void foo(int arr[static const restrict volatile 10]) {
        // static: the array contains at least 10 elements
        // const, volatile and restrict all apply to the array type.
    }
I imagine most of these depend on the C version, but this one specifically bit me because one tool only supported c99 and the other was c11 or something later.

Re: Mildly interesting quirks of C

#9

Post by veltas »

ainar-g wrote: post #7

Are there any practical cases where you'd want "extern void foo"?

You could use it for getting an address that will be linked in later. On GCC I get a warning (which I don't think I can mask) for taking the address of such an object, because its expression is type void. A better way of achieving this is usually to declare something like extern unsigned char foo[] instead, but that has a type other than void*.
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