GCC 指针转换警告
我想知道为什么 GCC 给我这个警告：
test.h: In function TestRegister:
test.h:12577: warning: cast to pointer from integer of different size
代码：
#define Address 0x1234
int TestRegister(unsigned int BaseAddress)
{
unsigned int RegisterValue = 0;
RegisterValue = *((unsigned int *)(BaseAddress + Address)) ;
if((RegisterValue & 0xffffffff) != (0x0 << 0))
{
return(0);
}
else
{
return(1);
}
}
I am wondering why GCC is giving me this warning:
test.h: In function TestRegister:
test.h:12577: warning: cast to pointer from integer of different size
Code:
#define Address 0x1234
int TestRegister(unsigned int BaseAddress)
{
unsigned int RegisterValue = 0;
RegisterValue = *((unsigned int *)(BaseAddress + Address)) ;
if((RegisterValue & 0xffffffff) != (0x0 << 0))
{
return(0);
}
else
{
return(1);
}
}
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评论（3）
可能是因为您使用的是 64 位平台，其中指针是 64 位，但
int是 32 位。经验法则：不要尝试使用整数来存储地址。
Probably because you're on a 64-bit platform, where pointers are 64-bit but
ints are 32-bit.Rule-of-thumb: Don't try to use integers to store addresses.
如果包含
gcc -Wall -std=c99您可以进行转换intptr_t这是一个与指针大小相同的整数类型。If you include
<stdint.h>and if you compile for the C99 standard usinggcc -Wall -std=c99you could cast to and fromintptr_twhich is an integer type of the same size as pointers.除此之外，您假设指针适合到
unsigned int，而C没有提供这样的保证......有一个数字今天使用的平台中有很多这是不真实的，显然包括您的平台。指向数据的指针可以安全地存储在
(void*)或 (type*) 中。可以将指针添加到（或减去）size_t或ssize_t。sizeof(int)、sizeof(size_t)、sizeof(ssize_t)和(void*)< 之间不存在保证关系/code> 或 (type*)...（此外，在这种情况下，初始化 var 并在下一行覆盖它没有实际意义...）
也无关，但您意识到
!= (0x0 << 0)→!= 0并且可以省略，因为if (x)=if (x != 0 ）...？也许这是因为这是从更大的样本中截取的，但是整个例程可以表示为（编辑：更改为
unsigned int*因为他似乎更有可能想跳过int大小的偏移量？）Among other things, you're assuming that a pointer will fit into an
unsigned int, where C gives no such guarantee… there are a number of platforms in use today where this is untrue, apparently including yours.A pointer to data can be stored in a
(void*)or (type*) safely. Pointers can be added to (or subtracted to yield) asize_torssize_t. There's no guaranteed relationship betweensizeof(int),sizeof(size_t),sizeof(ssize_t), and(void*)or (type*)…(Also, in this case, there's no real point in initializing the var and overwriting it on the next line…)
Also unrelated, but you realise that
!= (0x0 << 0)→!= 0and can be omitted, sinceif (x)=if (x != 0)… ? Perhaps that's because this is cut down from a larger sample, but that entire routine could be presented as(Edited: changed to
unsigned int*as it seems far more likely he wants to skip through atint-sized offsets?)