使用动态成员创建全局结构

Question

I have something like the following:

struct t{
    char arr[variable_len];
    int i;
};

int main(int argc, char *argv[]){
    // set size of arr to length of argv[1]
}

Is there a way to do this? I was originally just going to have arr be a pointer to an array and allocate the array separately, but this created massive issues due to the fact that I want to write this struct to a pipe (the pointer would get written and not the actual array).

Answer 1

Setting aside the lack of error checking, you could do the following...

struct t
{
    int i;
    int data_len;
    char arr[];
};

int main( int argc, char* argv[] )
{
    int data_len = atoi( argv[1] );
    struct t* var;

    var = malloc( sizeof( struct t ) + data_len );
    var->data_len = data_len;

    // open a pipe and do cool stuff to var

    fwrite( var, sizeof( struct t ) + var->data_len, 1, output_pipe );

    free( var );
}