Memory test fails on 2 byte accesses about rev HOT 3 CLOSED

#include <stdio.h>
#define u16 unsigned short
#define u8 unsigned char
#define assert(x) if (!(x)) { asm(".byte 0x00"); asm(".byte 0x00"); asm(".byte 0x00"); asm(".byte 0x00"); }

/* Memory to test */
#define SIZE 10000
u8 mem[SIZE];

#define fill_stride_f(type) void fill_stride_by_##type(type *addr, size_t size, type pattern, size_t idx, size_t stride) \
{ \
        for (size_t i = idx; i < size; i += stride) \
                addr[i] = pattern; \
}

fill_stride_f(u16);

#define check_stride_f(type) int check_stride_by_##type(type *addr, size_t size, size_t idx, type pattern, size_t stride) \
{ \
        int ret  = 0; \
        for (size_t i = idx; i < size; i += stride) \
                ret |= (addr[i] != pattern); \
        return ret;\
}

check_stride_f(u16);

int main(){
        u16 *addr =(u16*) mem;
        size_t size = SIZE/sizeof(u16);
        int ret = 0;
        const size_t stride = 16;

        for (size_t idx = 0; idx < stride; idx++) {
                fill_stride_by_u16((u16*)addr, size / 2, idx, idx, stride);
                ret |= check_stride_by_u16((u16*)addr, size / 2, idx, idx, stride);
        }
        assert(!ret);
        return 0;
}