Assignment of struct array

Question

    extern struct aStruct aStruct_table[4];
    
int main()
{
        aStruct_table[0].val1 = 0;
        aStruct_table[0].val2 = 0x0;
        aStruct_table[0].val3 = 0x130;
        aStruct_table[1].val1 = 1;
        aStruct_table[1].val2 = 0x140;
        aStruct_table[1].val3 = 0x860;
        aStruct_table[1].val1 = 4;
        aStruct_table[1].val2 = 0x2050;
        aStruct_table[1].val3 = 0x1950;
        aStruct_table[1].val1 = 7;
        aStruct_table[1].val2 = 0x6000;
        aStruct_table[1].val3 = 0x666;
}

Is there another way to assign the struct array without having so much code? Maybe sth like

    extern struct aStruct aStruct_table[4] = {{0,0x0,0x130},
                                             {1,0x140,0x860},
                                             {4,0x2050,0x1950},
                                             {7,0x6000,0x666}};

Jens Gustedt · Accepted Answer · 2011-12-17 22:50:39Z

4

You are mixing up assignment and initialization, I guess.

In modern C, AKA C99, the best way to do initialization of a struct is with "designated initializers"

struct aStruct A = { .val1 = 0, .val2 = 0x0A };

and the syntax for arrays of structs is just to repeat that:

struct aStruct B[] = {
   { .val1 = 0, .val2 = 0x0A },
   { .val1 = 2, .val2 = 0x0B }
};

But you shouldn't do it with the extern in front. That one is for the forward declaration in the header file without the initialization part.

If you really meant assignment, for struct you can use "compound literals

A = (struct aStruct){ .val1 = 0, .val2 = 0x0A };

but as you probably know there is no assignment syntax for arrays.

answered Dec 17, 2011 at 22:50

Jens Gustedt

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3 Comments

fge Over a year ago

an "assignment syntax for arrays"

Jens Gustedt Over a year ago

You mean there is one? Try it. As I say there is initialization syntax for arrays, my variable B shows that. But there is no such thing as assignment to arrays.

fge Over a year ago

OK, I mixed up between initialization and assignment, but you can initialize particular indices and skip others. Bah, nevermind.

fge · Accepted Answer · 2011-12-17 23:09:52Z

3

Yes, it is perfectly legal to do that.

With C99 initializers it can be even clearer:

extern struct aStruct aStruct_table[4] = {
    [0] = {
        .val1 = 0,
        .val2 = 0x0,
    },
    [1] = {
// etc etc

edited Dec 17, 2011 at 23:09

answered Dec 17, 2011 at 21:41

fge

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1 Comment

fge Over a year ago

@JensGustedt I forgot the dots to struct initalizers, apart from that it is perfectly valid!

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