Initialize/reset struct to zero/null

struct x {
    char a[10];
    char b[20];
    int i;
    char *c;
    char *d[10];
};

I am filling this struct and then using the values. On the next iteration, I want to reset all the fields to 0 or null before I start reusing it.

How can I do that? Can I use memset or I have to go through all the members and then do it individually?

Define a const static instance of the struct with the initial values and then simply assign this value to your variable whenever you want to reset it.

For example:

static const struct x EmptyStruct;

Here I am relying on static initialization to set my initial values, but you could use a struct initializer if you want different initial values.

Then, each time round the loop you can write:

myStructVariable = EmptyStruct;

The way to do such a thing when you have modern C (C99) is to use a compound literal.

a = (const struct x){ 0 };

This is somewhat similar to David's solution, only that you don't have to worry to declare an the empty structure or whether to declare it static. If you use the const as I did, the compiler is free to allocate the compound literal statically in read-only storage if appropriate.

Better than all above is ever to use Standard C specification for struct initialization:

struct StructType structVar = {0};

Here are all bits zero (ever).

Initialize/reset struct to zero/null

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