Char array error, expected an expression, error

Question

I have the following code, I want to initialize the char array to NULL.

getting the following error

error: expected an expression g_device->name1[NAME_LENGTH-1] = {'\0'};

typedef struct device_ {

    uint32_t id;
    char name1[NAME_LENGTH];
    char name2[NAME_LENGTH];

} device_t;

device_t  *g_device = NULL;


void init_device(void)
{

    g_device = malloc(sizeof(device_t));
    g_device->id = 0;
    g_device->name1[NAME_LENGTH-1] = {'\0'};
    g_device->name2[NAME_LENGTH-1] = {'\0'};
}

{'\0'} is not a valid expression in C. You probably want g_device->name1[0] = '\0'; (note, place '\0' in the beginning). — n. m. could be an AI
– n. m. could be an AI, Commented Jun 29, 2016 at 7:12

2501 · Accepted Answer · 2016-06-29 07:30:28Z

3

You cannot assign arrays in C, plus the types don't match anyway, g_device->name1[NAME_LENGTH-1] is a char and {'\0'} is a char[1].

Use strcpy:

strcpy( g_device->name1 , "" );

or manually terminate the array:

g_device->name1[0] = '\0';

Notice that you should set the first character to 0, not the last.

The above two examples will of course leave other elements uninitialized, so if you wanted to initialized them to 0, use memset or a loop:

memset( g_device->name , '\0' , NAME_LENGTH * sizeof( char ) );

or:

for( size_t index = 0 ; index < NAME_LENGTH * sizeof( *g_device->name ) ; index++ )
{
    g_device->name[index] = '\0';
}

edited Jun 29, 2016 at 7:30

answered Jun 29, 2016 at 7:10

2501

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Comments

sb9 · Accepted Answer · 2016-06-29 07:22:51Z

0

You can also use calloc to allocate the buffer, i.e.

g_device = calloc(1, sizeof(device_t));

This will allocate a buffer, which is completly filled with Zeroes, i.e. there's no need for further initialization of the character array.

edited Jun 29, 2016 at 7:22

answered Jun 29, 2016 at 7:17

sb9

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2 Comments

Kusalananda Over a year ago

Zeroes, not NULL. And the zeroes are interpreted like nul (\0). (nitpick)

sb9 Over a year ago

You're right, my answer was imprecise at this point. I adapted the answer

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