asked on

Is it possible to add pointer to void to unsigned short?

Is it possilbe to add pointer to void to unsigned short?

extern void * memcpy(void *, const void *, size_t);

unsigned char
somefunc_validate(void *data,
unsigned_16 validate_entries,
void *validate_cfg
) {
..
..

unsigned short min_value;

..

memcpy(&max_value, validate_cfg + sizeof(min_value), sizeof(max_value));

What is the result of: validate_cfg + sizeof(min_value)

Above is working code but after compiling with upgraded compiler, following error occurs:
illegal type(s): ptr-to-void '+' unit

SOLUTION

w00te

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w00te

Oh, I think you might be able to in C though. Maybe you switched to a C++ compiler which woudln't allow it?
gcc would like it and g++ wouldnt I think.
-w00te

naseeam

ASKER

I didn't switch to c++ compiler. I switched from WindRiver diab 4.2b C langauage compiler to WindRiver diab 5.8.0.0 C languge compiler.

How can this error be fixed without changing functionality? Maybe a typecast is needed.
I don't want to change the pointer arithemetic functionality but I need help in resolving this error.

ASKER CERTIFIED SOLUTION

jkr

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w00te

This works, change it to a char pointer before changing the arithmetic, they have the same internal representation aparently.
http://www.velocityreviews.com/forums/t316242-void-pointer-arithmetic.html
-w00te

int main() {
    void* someptr;
    int x = 14;
    someptr = &x;
  
    unsigned short someshort = 12;

    printf("%d", someptr);

    //conversion here, its the only important part.
    char* temp = (char*)someptr;
    temp += someshort;
    someptr = (void*)temp;

    printf("%d", someptr);

}

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w00te

Whoops, he beat me to it haha. Sorry bout that JKR.

naseeam

ASKER

Thanks for all the effort and comments.