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Re: return'ing a struct and trap representations
From: |
Paul Eggert |
Subject: |
Re: return'ing a struct and trap representations |
Date: |
Sun, 24 Sep 2006 23:01:07 -0700 |
User-agent: |
Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux) |
>> Should be: for integer and pointer types there are _no_ "trap
>> representations".
>
> I don't think that is guaranteed by C99.
That's correct. As I recall, only unsigned char objects are
guaranteed to be free of trap representations.
> Certainly the practical value of this for gnulib is questionable.
I've heard that some C implementations do support trap representations
of pointers in hardware, and that some debugging C implementations
also have trap representations for integers. See, for example
<http://www-128.ibm.com/developerworks/power/library/pa-ctypes3/>.
I've never knowingly used such implementations, thought I wouldn't be
surprised if I used one without knowing it.