gcc member initialization in array of struct

Question

how do you initialize only one member of a structure when you create an array of if, and when you are using GCC?, for example:

#define UNUSED OxFF
typedef struct inputs{
    uint8_t state;
    uint8_t limit;
    uint8_t value;
} INPUT_TYPE;

//create array but just care that all members .state are UNUSED
INPUT_TYPE Node1[5] ={ Node1.state = UNUSED }

The initialization refers to the array bu not to the member of the struct. Of course a loop could be used, but I don't want to initialize at run-time with an "input_init" function.

score 4 · Answer 1 · edited May 23 '17 at 11:52

4

The syntax for initializing certain members is a C99 feature. You're close, try this one:

#define UNUSED OxFF
typedef struct inputs{
    uint8_t state;
    uint8_t limit;
    uint8_t value;
} INPUT_TYPE;

INPUT_TYPE Node1[5] = {
    {.state = UNUSED},
    {.state = UNUSED},
    {.state = UNUSED},
    {.state = UNUSED},
    {.state = UNUSED}
};

See: How to initialize a struct in accordance with C programming language standards

Edit:

As I wasn't clear enough, I edited the answer.

How array initialization work, was answered here: How to initialize all members of an array to the same value?

edited May 23 '17 at 11:52

Community

1
1

answered Feb 03 '13 at 09:04

Sam

7,778
1
23
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This will only set `Node1[0].state == UNUSED`. The `.state` member for all other elements will be set to zero. – Michael Burr Feb 03 '13 at 09:21
I found it at last in [link]http://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Designated-Inits.html#Designated-Inits its a combination of two cases. – Lorenzo Gonzales Feb 04 '13 at 14:33
1

`INPUT_TYPE Node1[5] = { [0 ... 4].state = UNUSED }` It works fine – Lorenzo Gonzales Feb 04 '13 at 14:46

score 4 · Answer 2 · answered Feb 05 '13 at 06:32

4

I found it at last in http://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Designated-Inits.html#Designated-Inits its a combination of two cases.

INPUT_TYPE Node1[5] = { [0 ... 4].state = UNUSED } it is usefull in large arrays.

answered Feb 05 '13 at 06:32

Lorenzo Gonzales

71
5

score 2 · Answer 3 · answered Feb 03 '13 at 09:19

Since UNUSED is a non-zero value, you'll need to specify the initializer for each element of the array if that's what you need:

INPUT_TYPE Node1[5] = { 
    {.state = UNUSED}, 
    {.state = UNUSED}, 
    {.state = UNUSED}, 
    {.state = UNUSED}, 
    {.state = UNUSED}
};

score 0 · Answer 4 · answered Feb 03 '13 at 09:13

0

Why not use a constructor for init:

#define UNUSED OxFF
typedef struct inputs{
    uint8_t state;
    uint8_t limit;
    uint8_t value;

   inputs(){state = UNUSED, limit, value;};

} INPUT_TYPE;

?

answered Feb 03 '13 at 09:13

Leo Chapiro

13,678
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gcc member initialization in array of struct

4 Answers4