warning: cast to pointer from integer of different size

Hi

I'm sure this is a simple problem but I'm quite stuck, when ever I compile my code I get the "warning: cast to pointer from integer of different size" warning. Could someone show me how to cast/point or address the variable to stop it, thanks :D

The WriteUserData function requires a uint8_t data array type to work.

Code:

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typedef struct {
 
        uint64_t MacAddress;
        uint64_t RootMacAddress;
        uint16_t PANId;
        uint8_t device_Type;

} PACK configData_t;

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Code:

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int setConfigData(configData_t *cfg_dta) {

        uint8_t success = 0;

        if (WriteUserData(0, (uint8_t*)cfg_dta->MacAddress, 8, (void*)WriteCallback) != SUCCESS) {
                success = -1;
        } // if

return success;
}

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So, do you actually want to use MacAddress as the address of a location in memory, or do you want to pass the location containing MacAddress as a pointer?

Code:

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(uint8_t*)cfg_dta->MacAddress

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makes MacAddress - as it is - into a pointer.

Code:

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(uint8_t*)&cfg_dta->MacAddress

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Makes the location in memory of MacAddress into a uint8_t pointer.

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Mats

ah ha! option number two works, many thanks - I was really stuck on that!

:D

David

Quote:

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Originally Posted by DavidDobson

ah ha! option number two works, many thanks - I was really stuck on that!

:D

David

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beware that sometimes "Work != Correct", but I guess in this case "Work == Correct".

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Mats

Some warnings in C are not really warnings, but errors. That is semantically speaking, since they are compiler warnings, but are semantically incorrect.
Remember that well. This is especially true when pointers are involved. If the code is correct, then you will get no warnings at all.

Quote:

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Originally Posted by Elysia

Some warnings in C are not really warnings, but errors. That is semantically speaking, since they are compiler warnings, but are semantically incorrect.
Remember that well. This is especially true when pointers are involved. If the code is correct, then you will get no warnings at all.

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Well, in this case, it's a warning because the compiler says "I can do this, but I doubt it's what you wanted". Warnings aren't a good idea - it usually means that you are doing something wrong, just like an error. But it's not an error, because the compiler IS capable of actually doing what is asked for. For example, a 64-bit integer can hold a 32-bit pointer without any trouble at all - so a cast from a 64-bit integer to a 32-bit pointer COULD be correct code - it may have been written on a system where pointers are 64-bit, and thus needed to be stored in a 64-bit integer [ok, so we can debate whether storing pointers as integers is EVER a good idea, but unfortunately, some people do think it is a good idea, so we can't just forbid such casts].

In C++, you would probably want to use a reinterpret_cast<uint8_t *>(...) to do the same thing, and I expect that Visual Studio gives exactly the same warning if you put a 64-bit integer in () on such cast - but it is perfectly valid C++ code in all other respects [assuming of course that we end up with a valid address in the pointer if the pointer is ever dereferenced].

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Mats

Yes, hence semantically incorrect, but compiler correct.
Just because they are warnings does not mean your code is correct. One should beware of warnings, that's all I wanted to add. Especially in C.