Initialise 2 dimensional array of struct with all values zeroed

Question

Firstly I should say that I have very little C experience, and when I say very little I mean about 2 1/2 hours. So please forgive and correct any inaccuracies, stupidities, or other personal failings.

Here is the code as it currently stands:

typedef struct
{
    float n;
    int x;
    int y;
    int values[5];
} Cell;

typedef Cell Grid[10][10];

void update(Grid *source)
{
    // This should be a 2D array of Cells.
    // All the values in the Cell should be 0,
    // including the contents of the values array.
    Grid grid;
}

Update will be called fairly frequently and is somewhat performance critical, so I am willing to sacrifice some readability/simplicity/coding time if required for the sake performance. No, this is not premature optimisation.

Thanks for any help,

Sam.

Jack · Accepted Answer · 2014-01-02 04:35:37Z

2

The easiest and fastest way would be to memset the array:

memset(grid, 0 sizeof(Cell)*10*10);

Actually size of grid is known at compile time so

memset(grid, 0, sizeof(Grid));

should be enough.

answered Jan 2, 2014 at 4:35

Jack

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1 Comment

SeriousSamP Over a year ago

Thanks, this seems to be the best answer to the question and I will mark it as such. As it happens I had already tried this and concluded that it wasn't working, but upon further investigation it appears that the erroneous behaviour the code is exhibiting is from another, as yet unknown source. I'll continue investigation independently for now.

Digital_Reality · Accepted Answer · 2014-01-02 04:38:12Z

1

This will initialize your array.

Grid grid={0};

answered Jan 2, 2014 at 4:38

Digital_Reality

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2 Comments

Jonathan Leffler Over a year ago

The trouble with that is that some versions of GCC under some commonly used levels of warning (such as -Wall) will complain about 'incomplete initializers'. It shouldn't, but it does.

Digital_Reality Over a year ago

@JonathanLeffler yes. I tried with couple of compilers. I worked fine. But yes as you said, it should not give warning.

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