I have a struct
like this
typedef struct _somestruct {
int a;
int b;
}SOMESTRUCT,*LPSOMESTRUCT;
I am creating an object for the struct
and trying to print it's address like this
int main()
{
LPSOMESTRUCT val = (LPSOMESTRUCT)malloc(sizeof(SOMESTRUCT));
printf("0%x\n", val);
return 0;
}
..and I get this warning
warning C4313: 'printf' : '%x' in format string conflicts with argument 1 of type 'LPSOMESTRUCT'
So, I tried to cast the address to int
like this
printf("0%x\n", static_cast<int>(开发者_运维百科val));
But I get this error:
error C2440: 'static_cast' : cannot convert from 'LPSOMESTRUCT' to 'int'
What am I missing here? How to avoid this warning?
Thanks.
%x
expects an unsigned. What you're printing is a pointer. To do that correctly, you normally want to use %p
. To be pedantically correct, that expects a pointer to void, so you'll need to cast it:
printf("%p\n", (void *)val);
In reality, most current implementations use the same format for all pointers, in which case the cast will be vacuous. Of course, given the C++ tag, most of the code you've included becomes questionable at best (other than the parts like LPSOMESTRUCT, which are questionable regardless). In C++, you normally want something more like:
struct somestruct {
int a;
int b;
};
somestruct *val = new somestruct; // even this is questionable.
std::cout << val;
Use the %p format specifier to print a pointer.
printf("%p\n", val);
If you want to cast then using reinterpret_cast instead of static_cast might do the trick here.
With printf try using the %zu instead of %x for printing out a pointer because the pointer is of unsigned integer type (ie %zu).
printf("%zu \n", val);
Just one other thing, being a c++ program is there a reason why you are using malloc instead of new?
As this is tagged C++, can I just point out that you do not need typedefs when creating structs in that language:
typedef struct _somestruct {
int a;
int b;
}SOMESTRUCT,*LPSOMESTRUCT;
should be:
struct SOMESTRUCT {
int a;
int b;
};
Also, it is considered by many to be bad practice to create typedefs like LPSOMESTRUCT which hide the fact that a type is a pointer.
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