[patch] Add a section about implementation-defined behavior to the user's manual

[Richard Smith]

On Tue, Jan 29, 2013 at 4:47 PM, Nico Weber <thakis at chromium.org> wrote:
> On Tue, Jan 29, 2013 at 1:00 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>> On Tue, Jan 29, 2013 at 10:16 PM, Nico Weber <thakis at chromium.org> wrote:
>>> a coworker asked me if clang documents how it handles right shifts of
>>> signed numbers today. As far as I can tell there's no documentation
>>> for this, but I found PR11272 about documenting implementation-defined
>>> behavior. The bug suggests just linking to gcc's documentation as a
>>> first step, which is what the attached patch does. This isn't quite
>>> correct (for example, clang supports UCNs without any flags), but is
>>> correct for most things. People can fill in more details over time.
>>
>> +clang generally matches `gcc's implementation-defined
>> +behavior <http://gcc.gnu.org/onlinedocs/gcc-4.2.1/gcc/C-Implementation.html#C-Implementation>`.
>>
>> Maybe there's a different wording that does not promise too much?  I
>> can easily see users relying on this (or complaining about Clang's
>> implementation-defined behavior being different from gcc's).
>
> "generally tries to match"? The "generally" sounded fairly
> weasel-wordy to me already.
>
>> What might help is a list of implementation-defined behaviors with
>> quotations from the standard, as a boilerplate for developers to fill
>> in.  (It is much easier to write documentation when you know what
>> exactly you should describe.)
>
> I don't have a copy of the standard.

Latest working draft in committee mailing:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3485.pdf

Current working draft:

https://github.com/cplusplus/draft