Three-dimensional array initialization

Question

In a bit of code I'm looking at, a 3D array has been initialized like so:

static const char codeset[6][256][10] = {
 [0] = { [0x20] = " ",
 [0x21] = "!",
 [0x22] = """,
 [0x23] = "#",
}};

(It does go on to initialize the rest of the cells, I've cut it short to show something readable.)

This does not compile. Is it supposed to? What's going on here?

• Antoine Pelisse: Could we have the error message ?
• dkb: syntax error : '[', pointing to the line with [0].
• Kos: Compiles for me correctly (gcc 4.5.1). If you're on GCC, you can add -std=c99 to your command line just to be on the safe side, as it's a C99 extension.
• dkb: Alas, I'm in Visual studio, and apparently it's not going to work there: eggheadcafe.com/software/aspnet/34012666/…

Answer 1

You are using C99 initializers, but your compiler does not support C99 or C99 is not enabled.

Answer 2

You are trying to use C99 initializers, but most likely your compiler isn't C99-compliant, otherwise it would work.

• Kos: Good link, but unless my reading skills are bugged, it states that it's C99 extension, not GCC extension. GCC extends upon this by allowing to initialize ranges. +1 anyway as the link explains what's going on here. I didn't know that one too :)
• qrdl: @Kos Thanks, corrected. I was so much sure it is GCC-only so I didn't read thoughtfully.

Answer 3

As a guess, it trying to create the "alphabet" for xml string ASCII data. The " (double quote) character in xml is represented as &quot. So the [0][0 - 255] group is xml.

It looks like an equivalence table. It translates from xml to ASCII or whatever.

• dkb: Heh, maybe I was unclear - I know what the point of the array is, I want to know what's the problem with the initialization (Which, from what I've read, isn't actually supposed to work like that).