F********g
发帖数: 475 | 1 http://www.gowrikumar.com/c/
The following C program segfaults of IA-64, but works fine on IA-32.
int main()
{
int* p;
p = (int*)malloc(sizeof(int));
*p = 10;
return 0;
}
Why does it happen so?
是不是CONSTANT LITERAL被默认为８BYTE，COMPILER分配的指针指向４BYTE INT导致？
求点解！ |
p***o
发帖数: 1252 | 2 If your compiler is not that buggy, then the malloc implementation
is not standard conforming.
The malloc() and calloc() functions return a pointer to the
allocated memory that is *suitably aligned* for *any kind* of
variable.
【在 F********g 的大作中提到】
: http://www.gowrikumar.com/c/
: The following C program segfaults of IA-64, but works fine on IA-32.
: int main()
: {
: int* p;
: p = (int*)malloc(sizeof(int));
: *p = 10;
: return 0;
: }
: Why does it happen so?
|
F********g
发帖数: 475 | 3 Sounds like a bus error.
Still confused why it's a problem for 64 bit architecture.
【在 p***o 的大作中提到】
: If your compiler is not that buggy, then the malloc implementation
: is not standard conforming.
: The malloc() and calloc() functions return a pointer to the
: allocated memory that is *suitably aligned* for *any kind* of
: variable.
|
X****r
发帖数: 3557 | 4 you need to #include before using malloc, otherwise the implicit
declaration of this function may not match its implementation.
there is no point wasting time in puzzles like this.
【在 F********g 的大作中提到】
: http://www.gowrikumar.com/c/
: The following C program segfaults of IA-64, but works fine on IA-32.
: int main()
: {
: int* p;
: p = (int*)malloc(sizeof(int));
: *p = 10;
: return 0;
: }
: Why does it happen so?
|
w***g
发帖数: 5958 | 5 牛！
implicit
【在 X****r 的大作中提到】
: you need to #include before using malloc, otherwise the implicit
: declaration of this function may not match its implementation.
: there is no point wasting time in puzzles like this.
|
L***n
发帖数: 6727 | 6 说个无关的，点解就点解，求什么点解，不会广东话就别说了
【在 F********g 的大作中提到】
: http://www.gowrikumar.com/c/
: The following C program segfaults of IA-64, but works fine on IA-32.
: int main()
: {
: int* p;
: p = (int*)malloc(sizeof(int));
: *p = 10;
: return 0;
: }
: Why does it happen so?
|
a****l
发帖数: 8211 | 7 actually problems like this could be real-world puzzles that costs people
days of work time... And knowing the possible solutions like this is what I call "real programming experience".
implicit
【在 X****r 的大作中提到】
: you need to #include before using malloc, otherwise the implicit
: declaration of this function may not match its implementation.
: there is no point wasting time in puzzles like this.
|
c****p
发帖数: 6474 | 8 这个会导致seg fault么？
implicit
【在 X****r 的大作中提到】
: you need to #include before using malloc, otherwise the implicit
: declaration of this function may not match its implementation.
: there is no point wasting time in puzzles like this.
|
X****r
发帖数: 3557 | 9 Yes, because a implicitly declared function always returns 'int',
which may or may not be the same size as 'void *', which is the
actual return type of 'malloc'. If they are of different sizes,
say 'int' is 32-bits while 'void *' is 64-bits, the result from
malloc is cut-off by half before used as a pointer, which would
surely result in seg fault.
Note that both C99 and C++ disallow implicit function declarations,
and the compiler is probably going to warn you even if you compile
in C90. Implicit function declarations are relics from K&R. Just
don't do it.
【在 c****p 的大作中提到】
: 这个会导致seg fault么？
:
: implicit
|
F********g
发帖数: 475 | 10 Just found out that the default supported standard by gcc is
gnu89....zzzzz
Thank you for you pointer. Have a good weekend.
【在 X****r 的大作中提到】
: Yes, because a implicitly declared function always returns 'int',
: which may or may not be the same size as 'void *', which is the
: actual return type of 'malloc'. If they are of different sizes,
: say 'int' is 32-bits while 'void *' is 64-bits, the result from
: malloc is cut-off by half before used as a pointer, which would
: surely result in seg fault.
: Note that both C99 and C++ disallow implicit function declarations,
: and the compiler is probably going to warn you even if you compile
: in C90. Implicit function declarations are relics from K&R. Just
: don't do it.
|
|
|
j*a
发帖数: 14423 | 11 always use -Wall?
【在 F********g 的大作中提到】
: Just found out that the default supported standard by gcc is
: gnu89....zzzzz
: Thank you for you pointer. Have a good weekend.
|
c****p
发帖数: 6474 | 12 我在64位平台上跑没问题。
把p打出来也是64位的地址。【 在 Xentar (思考猪) 的大作中提到: 】 |
N***m
发帖数: 4460 | 13 相信思考朱德。
套用C++ faq的一句话，
不要说在你的机器上，用你的程序经过编译器编译后能跑，
just don't do it！
【在 c****p 的大作中提到】
: 我在64位平台上跑没问题。
: 把p打出来也是64位的地址。【 在 Xentar (思考猪) 的大作中提到: 】
|
c****p
发帖数: 6474 | 14 代码：
int main()
{
int* p;
p = 0;
p = (int*)malloc(sizeof(int));
printf("%dbits: %x\n", sizeof(p), p);
*p = 10;
return 0;
}
结果：
8bits: 1bf3010
这个结果不能说明malloc的返回值是32位的int啊。
【在 N***m 的大作中提到】
: 相信思考朱德。
: 套用C++ faq的一句话，
: 不要说在你的机器上，用你的程序经过编译器编译后能跑，
: just don't do it！
|
t****t
发帖数: 6806 | 15 你这显然验证了xentar的说法啊. 一个好好的地址只剩低32位了.
我为什么要浪费时间发这么个贴子.
啊我知道了, 你不会数数!
【在 c****p 的大作中提到】
: 代码：
: int main()
: {
: int* p;
: p = 0;
: p = (int*)malloc(sizeof(int));
: printf("%dbits: %x\n", sizeof(p), p);
: *p = 10;
: return 0;
: }
|
l******d
发帖数: 530 | 16 我还真碰到类似问题，忘记include头文件，编译过了，结果就是不对，花了好久时间
才发现。 |
c****p
发帖数: 6474 | 17 - -
【在 t****t 的大作中提到】
: 你这显然验证了xentar的说法啊. 一个好好的地址只剩低32位了.
: 我为什么要浪费时间发这么个贴子.
: 啊我知道了, 你不会数数!
|
k***5
发帖数: 583 | 18 去了这个网站看了看，很多puzzle属于基本违背了编程规范的东西。当然你可以费力气
去弄清楚，不过容易的答案就是follow编程规范。 |
L***n
发帖数: 6727 | 19 这种问题最好的解决方法应该是写个预处理程序检查源代码，不合规范的指出来，
而不是事后犯错误后绞尽脑汁去想可能的原因。
【在 k***5 的大作中提到】
: 去了这个网站看了看，很多puzzle属于基本违背了编程规范的东西。当然你可以费力气
: 去弄清楚，不过容易的答案就是follow编程规范。
|
F********g
发帖数: 475 | 20 有助于弄清LANGUAGE SPEC。
C９９标准俺是看不下去的ZZ。。
【在 L***n 的大作中提到】
: 这种问题最好的解决方法应该是写个预处理程序检查源代码，不合规范的指出来，
: 而不是事后犯错误后绞尽脑汁去想可能的原因。
|
