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Demonstrating a gcc bug using __attribute__((packed)) on SPARC
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#include <stdio.h> | |
#include <stddef.h> | |
int main(void) | |
{ | |
struct foo { | |
char c; | |
int x; | |
} __attribute__((packed)); | |
struct foo arr[2] = { { 'a', 10 }, {'b', 20 } }; | |
int *p0 = &arr[0].x; | |
int *p1 = &arr[1].x; | |
printf("sizeof(struct foo) = %d\n", | |
(int)sizeof(struct foo)); | |
printf("offsetof(struct foo, c) = %d\n", | |
(int)offsetof(struct foo, c)); | |
printf("offsetof(struct foo, x) = %d\n", | |
(int)offsetof(struct foo, x)); | |
printf("arr[0].x = %d\n", arr[0].x); | |
printf("arr[1].x = %d\n", arr[1].x); | |
printf("p0 = %p\n", (void*)p0); | |
printf("p1 = %p\n", (void*)p1); | |
printf("*p0 = %d\n", *p0); | |
printf("*p1 = %d\n", *p1); | |
return 0; | |
} | |
/* | |
Output on x86 Ubuntu, gcc 4.5.2: | |
sizeof(struct foo) = 5 | |
offsetof(struct foo, c) = 0 | |
offsetof(struct foo, x) = 1 | |
arr[0].x = 10 | |
arr[1].x = 20 | |
p0 = 0xbfbab5ff | |
p1 = 0xbfbab604 | |
*p0 = 10 | |
*p1 = 20 | |
Output on SPARC Solaris 9, gcc 4.2.1: | |
sizeof(struct foo) = 5 | |
offsetof(struct foo, c) = 0 | |
offsetof(struct foo, x) = 1 | |
arr[0].x = 10 | |
arr[1].x = 20 | |
p0 = ffbff317 | |
p1 = ffbff31c | |
Bus error | |
*/ |
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