Re: Xcode-users Digest, Vol 2, Issue 621
Re: Xcode-users Digest, Vol 2, Issue 621
- Subject: Re: Xcode-users Digest, Vol 2, Issue 621
- From: Wim Lewis <email@hidden>
- Date: Mon, 31 Oct 2005 14:44:07 -0800
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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