How pass(to function) by value variable size array? - c

Question

First of all I know that array A degrades to pointer when we call function f(int a[]) and f(int *p) is same.
BUT:
1.I really need sending by value all array.
2.I really need that sending size is non const in function (but const size in plase we calling function)
I write some example:
http://ideone.com/ZbW0wT
#include <stdio.h>
#define SZ 15
typedef struct {int a[SZ];} rec;
int main(){
void pa(rec);
int value[SZ] ={9,8,7,6,5,4,3,2,1,0};
pa(*(rec*)value);
printf("%u %u\n",sizeof(rec),sizeof(value));
return 0;
}
void
pa(rec b){
int z;
for(z=0;z<SZ;z++){
printf("array[%2d] is %d\n",z,b.a[z]);
}
}
This code work for const size , but how change so pa would get by value some rec which size depend on passed array?
Update: it must by value sended , but not const sized as in Pascal etc , but in true C way , all pass by value not by pointer on 0 element
and function need universal so user can write func(variablesizeArrayOfT) where arg passed by value.
if possible need standard way (C11 or better C99 or better C89 or better K&R), if cant then gcc
UPD2: http://ideone.com/H4XGqC
#include
typedef struct{
int len;
int a[];
} av;
void f(av a){
while(a.len--){
printf("array[%2d] is %d\n",a.len,a.a[a.len]);
}
}
int main(){
int b[]={3,1,2,3};
int c[]={7,1,2,3,4,5,6,7};
f(*(av*)b);
f(*(av*)c);
return 0;
}
all good by probably bug in alignment so size(3 and 7) is right but value of a[] is not
UPD3 see throw gcc -g -c 2ndSRC.c &&objdump -d -M intel -S 2ndSRC.o
it just send only size (b[0] and c[0]) but not all array

Answer 1

An idiomatic way to have arrays containing data of variable length in C is to use a buffer with a maximum size which is known at compile time, is that what you wanted?
#include <stdio.h>
#define MAX_SIZE 15
typedef struct {
int arr[MAX_SIZE];
size_t arr_len;
} rec_t;
void pa(rec_t rec){
for(int z=0; z<rec.arr_len; z++){
printf("array[%2d] is %d\n", z, rec.arr[z]);
}
}
int main(void){
rec_t rec ={
.arr = {9,8,7,6,5,4,3,2,1,0},
.arr_len = 10
};
pa(rec);
}