Structure initialization and clearing

[Roubles]

Hi All,

Quick question; what is the difference between initializing and
clearing a structure like this:

mystruct_t a = {0};


and initializing and clearing it like this:

mystruct_t a;

memset(a, 0, sizeof(mystruct_t));

TIA,
Roubles

 

[Kenneth Brody]

Hi All,

Quick question; what is the difference between initializing and
clearing a structure like this:

mystruct_t a = {0};

and initializing and clearing it like this:

mystruct_t a;

memset(a, 0, sizeof(mystruct_t));

In practice, probably not much.

However, suppose the first element of the struct were a pointer, and
you are on a system where a NULL pointer is not all-bits-zero.

Also, my understanding is that _all_ entries will be set to their zero
representation, which may not be all-bits-zero. (For example, a "double"
value.)

 

[Default User]

Hi All,

Quick question; what is the difference between initializing and
clearing a structure like this:

mystruct_t a = {0};

This sets each member of the structure to the equivalent of 0 for the
type. You can only intitialize this way, not assign.

and initializing and clearing it like this:

mystruct_t a;

memset(a, 0, sizeof(mystruct_t));

This sets the whole thing to all-bits 0. For some things like floating
point numbers or pointers, this could be the wrong thing.



Brian Rodenborn

 

[Joe Wright]

Hi All,

Quick question; what is the difference between initializing and
clearing a structure like this:

mystruct_t a = {0};


and initializing and clearing it like this:

mystruct_t a;

memset(a, 0, sizeof(mystruct_t));

TIA,
Roubles

The first is an initialization the compiler does for you and the
second is one you do yourself. You know that. What is the real
question? As an aside, I note that the prototype..

void *memset(void *buffer, int ch, size_t num);

...suggests to me..

memset(&a, 0, sizeof a);

...but of course, it's just style, right?

 

[Joe Wright]

Hi All,

Quick question; what is the difference between initializing and
clearing a structure like this:

mystruct_t a = {0};


and initializing and clearing it like this:

mystruct_t a;

memset(a, 0, sizeof(mystruct_t));

TIA,
Roubles

Note that a is a structure, not a pointer. You need &a to take its
address for memset().