Does a flexible array member increase sizeof a struct?

I have the following kind of code:

typedef struct
{    
    u32 count;
    u16 list[];   
} message_t;
...

message_t* msg = (message_t*)buffer;  
msg->count = 2;
msg->list[0] = 123;
msg->list[1] = 456;

size_t total_size = sizeof(*msg) + sizeof(msg->list[0]) * msg->count;  

send_msg( msg, total_size ); 

Problematic line is the line with sizeofs. I am not sure is that correct way to count needed space. Does sizeof(*msg) contains already something about the list member?

I can test it with my compiler, but does every compiler work similary in this case?