Global structure pointer initialization

Question

Structure definition

struct list
{
  struct list **next, **prev;
}

core.c

//Global struct
struct list *threads = {&threads, &threads};  //Warnings here:

// warning: initialization from incompatible pointer type
// warning: excess elements in scalar initializer
// warning: (near initialization for 'threads')

PS: I don't have a main function in this file. And this has to be global.

Kevin Reid · Accepted Answer · 2012-04-23 19:52:02Z

3

You need to initialize the pointer-to-struct-list variable threads with a pointer to a struct list. {&threads, &threads} is not a pointer to a struct list, but it could be a struct list.

In order to define an actual structure instance and obtain a pointer to it, you can use a compound literal and take its address:

struct list *threads = &((struct list){&threads, &threads});

(Note: compound literals ((type){initializer}) are a C99 feature; some compilers which haven't caught up to a 13-year-old standard may reject it.)

answered Apr 23, 2012 at 19:52

Kevin Reid

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2 Comments

code muncher Over a year ago

thanks Kevin, one more question, next to struct initialization, I have something like void* vp_threads = threads; // if I write &threads, this's fine but without '&' its giving me error 'initializer element is not constant' Why so? any idea?

Kevin Reid Over a year ago

I don't know, sorry. Those are two different pointers, of course. If you need help on that you should ask a separate question, and give more details on what you need to accomplish.

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