sizeof of string literal inside a struct - C

Question

I have the following code:

struct stest
{
    int x;
    unsigned char data[];
} x = 
{
    1, {"\x10\x20\x30\x00\x10"} 
};

int main()
{
    printf( "x.data: %d\n", (int)x.data[0] );
    return 0;
}

Which works fine. However, I need to use the size of the "data".

If I do:

printf( "sizeof x.data: %d\n", (int)sizeof(x.data) );

I get the error:

invalid application of ‘sizeof’ to incomplete type ‘char[]’

Is there a way to get the size of "data" in this situation, or maybe a suggestion of an alternative method I could use?

The compiler I am using is gcc 4.6.3.

Answer 1

Since x.data is a null terminated char array you could just use strlen function.

printf( "sizeof x.data: %u\n", strlen(x.data)+1 );

This code will not work correctly if the array contains null. In this case you need to store length of the array in separate member of struct.