allocate memory block and assign to a char array for send socket a memory block

Question

I have one question, and can not figure out how to do that after googling. I define a struct and use to allocate a memory block 4 alignment.

typedef struct
{
    unsigned int  param_len;
    char          param[1]; /* variable size array - param_len bytes */
    /* Up to 3 pad bytes follow here - to make the whole struct int aligned. */
} test_t;

test_t test;
test.param_len = 5; /* set param_len = 5 */

int alloc_len = ((test.param_len % 4) + 1) * 4; /* 8 for int aligned */

unsigned char *block = malloc (alloc_len); /* allocate 8 bytes */

how to assign the param to the 8 bytes memory block as the following diagram?

+------------+
| param_len  | int aligned
| param[1]   | 8 bytes
|            |
+------------+

If I do that:

&test.param[0] = block;

gcc complains error: lvalue required as left operand of assignment

If I do that:

test.param = block;

gcc complains error: assignment to expression with array type

Can any one help me to solve this problem? Thanks in advance.

EDIT:

My real question is how to write a code to assign a block of memory to the variable param1 and then send test by socket. So I try to use &test.param[0] = block;, but gcc complains lvalue required.

Solution:

After asking my classmate Daniel, he uses another apporach and then writes a test code sample_alloc.c for me. That what I real want.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct
{
    unsigned int  param_len;
    char          param[1]; /* variable size array - param_len bytes */
        /* Up to 3 pad bytes follow here - to make the whole struct int aligned. */
} test_t;

int main() {
    int param_len=5;
    int alloc_len = sizeof(unsigned int) + ((param_len % 4) + 1) * 4; /* 8 for int aligned */
    unsigned char *block = malloc (alloc_len); /* allocate 4 + 8 bytes */
    test_t *p=(test_t *)block;
    p->param_len = param_len;
    memcpy(p->param ,"Hello", 6);
    printf("%d %s\n", p->param_len, p->param);
}

Thanks, Daniel!