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| /**
*
Linux下对Alignment trap的处理有下面几种方式：
0 (ignored)
1 (warn)
2 (fixup)
3 (fixup+warn)
4 (signal)
5 (signal+warn)
使用方法：
# echo 3 > /proc/cpu/alignment
*/
#include <stdio.h>
#include <stdlib.h>
/// case 1
void fool(unsigned char* buf, int len)
{
unsigned int* p = (unsigned int*)buf;
int i;
for (i = 0; i < len; i++)
{
*p++ = i+1;
printf("%d ", *p);
}
}
void foolish()
{
unsigned char poor[100];
fool(poor, sizeof(poor)/sizeof(int));
}
// case 1 end
////////////////////////////////////////////////////////////////
/// case 2
struct rte_unpacked_struct_t
{
char c1;
int i;
char c2;
short s1;
char c3;
};
struct rte_packed_struct_t
{
char c1;
int i;
char c2;
short s1;
char c3;
}__attribute__((__packed__));
struct rte_unpacked_struct_t unpacked;
struct rte_packed_struct_t packed;
void print_addr()
{
printf("sizeof(unpacked) = %d sizeof(packed) = %d\n", sizeof(unpacked), sizeof(packed));
printf("Addr of unpacked: %p\n", &unpacked);
printf("Addr of unpacked.c1: %p\n", &unpacked.c1);
printf("Addr of unpacked.i: %p\n", &unpacked.i);
printf("Addr of unpacked.c2: %p\n", &unpacked.c2);
printf("Addr of unpacked.s1: %p\n", &unpacked.s1);
printf("Addr of unpacked.c3: %p\n", &unpacked.c3);
printf("Addr of packed: %p\n", &packed);
printf("Addr of packed.c1: %p\n", &packed.c1);
printf("Addr of packed.i: %p\n", &packed.i);
printf("Addr of packed.c2: %p\n", &packed.c2);
printf("Addr of packed.s1: %p\n", &packed.s1);
printf("Addr of packed.c3: %p\n", &packed.c3);
}
short* rte_get_s1(void)
{
return &unpacked.s1;
}
void case2()
{
print_addr();
int* val = (int *)rte_get_s1();
printf("val = %d\n", *val);
}
/// case 2 end
////////////////////////////////////////////////////////////////
/// case 3
struct foo_t
{
short a;
short b;
short c;
short d;
};
struct foo_t foo;
short* get_foo_c(void)
{
return &foo.c;
}
void case3()
{
printf("sizeof(foo) = %d\n", sizeof(foo));
// 注意！！此处将short*强制转换为int*，造成出错
int* val = (int *)get_foo_c();
printf("val: %d\n", *val);
}
// case 3 end
//////////////////////////////////////////////////////////////
/// case 4
void case4()
{
char* str = "01234567";
unsigned* u = (unsigned *)(str+1);
printf("0x%08x\n", *u);
}
/// case 4 end
int main()
{
printf("test of alignment trap...\n");
//foolish();
//case2();
//case3();
case4();
return 0;
}
|
