Jagged array implementation in C- error: expected ';' at the end of declaration list

Question

I wrote a piece of C code as below:-

typedef struct {
    unsigned int buffer_ctrl[4];
    unsigned int buffer1[10];
    unsigned int buffer2[40];
    unsigned int buffer3[20];
    unsigned int buffer4[15];
    unsigned int *buffer_ptr[4] = {buffer1, buffer2, buffer3, buffer4};
    unsigned int canary[4];
} buffer_t;

I wrote this in a header file which I included in a main code. I had read up a lot of examples on jagged array in C and thought this would work just fine. One of the links was Do jagged arrays exist in C/C++?.

However, when I compile I get the error "expected ';' at end of declaration lsit". Can someone please help explain what might be the error here? Thanks!

It will except `unsigned int *buffer_ptr[4] = {buffer1, buffer2, buffer3, buffer4};` -- you can't initialize member of a struct at the time of definition. (but you could use a `union` within the `struct ` to essentially do the same). — David C. Rankin, Nov 13 '18 at 05:02
Yes, right -- you can't (that was meant to say all would work "except" ..). — David C. Rankin, Nov 13 '18 at 05:04
Please *copy-paste* the error message verbatim. This does not help anyone if you typo the error message! — Antti Haapala -- Слава Україні, Nov 13 '18 at 05:36
Thanks, it seems I was correct in thinking it was the initialization inside the struct that was the problem. I just wanted it confirmed that I was understanding things correctly. — Siddharth Kabra, Nov 13 '18 at 18:49

score 2 · Answer 1 · answered Nov 13 '18 at 05:16

2

You cannot assign to buffer_ptr within the definition of the buffer_t structure itself. You have to define a variable of the type buffer_t first and then assign to it.

You can do something like this:

buffer_t bt = {
    .buffer_ptr[0] = bt.buffer1,
    .buffer_ptr[1] = bt.buffer2,
    .buffer_ptr[2] = bt.buffer3,
    .buffer_ptr[3] = bt.buffer4
};

answered Nov 13 '18 at 05:16

P.W

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There generally isn't a good reason to permanently store an array that is so easy to calculate, though. You can create such an array when you need it, and save memory when you don't. – yyny Nov 13 '18 at 18:55

Jagged array implementation in C- error: expected ';' at the end of declaration list

1 Answers1