Easiest way to get two arrays have the same length?

Question

There are two arrays in my projects. One is of static const type which contain more or less entries on different projects, like

static const array_A[] = { ... };

I do not like the style of array_A[N] = { ... } since I do not want to count the length of array manually.

There is another array B whose length is required to be the same as A.

Some compiler (such as armcc) support the following trick

const int N = sizeof(array_A) / sizeof(array_A[0])
static const array_B[N];

But this trick fails with gcc compiler. So is there any other easy way ?

what do you mean by it fails? it clearly [works for me.](http://ideone.com/CTSfDl) — Zac Wrangler, Oct 15 '13 at 01:32
You are missing a type name in both your array declarations. — Charlie Burns, Oct 15 '13 at 01:32
@ZacWrangler, he tagged C, not c++. Code in C compiles with clang, not gcc. — Charlie Burns, Oct 15 '13 at 01:35

score 1 · Answer 1 · answered Oct 15 '13 at 01:36

1

Interesting that:

int a[] = {1, 2, 3};
const int N = sizeof(a)/sizeof(a[0]);
const int b[N];

Compiles with clang, does not compile with gcc 4.2.1:

error: variably modified ‘b’ at file scope

OP asked for C, not C++, so a fix for gcc would be

int a[] = {1, 2, 3};
const int b[sizeof(a)/sizeof(a[0])];

answered Oct 15 '13 at 01:36

Charlie Burns

It does work. So this should be a gcc bug? – Pan Ruochen Oct 15 '13 at 06:01
I would not call it a gcc bug. The C language has evolved over the years, and compilers struggle to keep up and they add extensions of their own. This feature may or may not be in any C specification, I don't know. You could ask SO if this feature is found in any official C spec if you were interested. – Charlie Burns Oct 15 '13 at 15:04

1 Answers1