Subject: Re: [boost] [AFIO] Formal review
From: John Bytheway (jbytheway+boost_at_[hidden])
Date: 2015-09-02 05:31:34
On 2015-09-01 18:42, Niall Douglas wrote:
> Please do correct me if I am wrong, but I had thought that this is
> defined behaviour:
> int a=5;
> void *b=(void *)(size_t) a;
> int c=(int)(size_t) b;
> This is certainly a very common pattern in C.
I believe this is implementation-defined. Based on N3797
[expr.reinterpret.cast], paragraph 5:
"A value of integral type or enumeration type can be explicitly
converted to a pointer. A pointer converted to an integer of sufficient
size (if any such exists on the implementation) and back to the same
pointer type will have its original value; mappings between pointers and
integers are otherwise implementation-defined."
The behaviour that is defined (pointer to integer and back) is the
reverse of the one you want.
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk