how to avoid compilation error: expression must be a modifiable lvalue

Hi.

I met a compilation error with following code. a physical buffer (communication buffer of MCU) tossed to void* dest. if I change all argument to local variable and pointer compilation successful.

First I thought, polyspace doesn't understand typecasting of void to other, but I guess now when physical address is tossed as argument then it occur compilation error "expression must be a modifiable lvalue", since polyspace doesn't understand physical address.

Am i thinking correct? and does anybody can help me to avoid compilation error?

typedef unsigned char u08;

void* AL_MemCpy  (void* dest, const void* source, u08 count)
{
  while (count--)
  {
       *((u08*)dest)++ = *((u08*)source)++;
  }
}

// used in other function like below

(void)AL_MEMCPY(RxBuffer,&(data[1]),(u08)RxMessage.Length);

Answer 1

[Jan]

(u8 *) dest is a temporary variable, which cannot be increased. Perhaps you want this:

*((u08*)dest++) = *((u08*)source++);

But this copies the first byte only. Perhaps memcpy would be smarter?

Or:

u08 *d = (u08 *) dest, *s = (u08 *) source;
while (count--) {
  *d++ = *s++;
}

[James Tursa]

+1 is for the last option shown, which I prefer since it is clear what is being done and avoids trying to apply the ++ operator to a (void *) type (which inherently doesn't make sense and isn't allowed since void is of unknown size) using fancy-mangled syntax (e.g., the first option shown above will not compile).

[Bong-Kee Choi]

Actually this code cause MISRA Rule violation also. Even though it can be work with some compiler (Codewarrior) but compatibility can't be guaranteed.

Thanks to all.