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Re: Xcode-users Digest, Vol 2, Issue 621

On 31 Oct, 2005, at 2:04 PM, George Warner wrote:
On Mon, 31 Oct 2005, Mark Dawson <email@hidden> wrote:
I'm taking on some older code, and I'm getting this warning: "warning: target
of assignment not really an lvalue; this will be a hard error in the future"

for the following line:

*((uint32_t*)dst)++ = *((uint32_t*)src)++;

Why is this code going to be an error in the future? 

Just use:

    *(uint32_t*)dst++ = *(uint32_t*)src++;

The typecasting has president over the post-increment operator. It will "do the right thing". (And not cause the warning ;-).

No, that'll do something else --- it would be equivalent to
*(uint32_t *)(dst++) = *(uint32_t*)(src++);
which will leave dst and src with different values after the increments than if they'd been cast to uint32, unless they happened to already be pointing to a type with the same width as a uint32.

As Steve Checkoway points out the problem is not that *(type *)foo is being used as an lvalue in the assignment, but that ((type *)foo) is being used as an lvalue by the ++ operator. The warning message is a little misleading.



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 >Re: Xcode-users Digest, Vol 2, Issue 621 (From: George Warner <email@hidden>)



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