[cfe-dev] [LLVMdev] Reminder: 3.6 branch is coming

[Nikola Smiljanic]

Count me in for testing Fedora and OpenSUSE.

On Tue, Jan 13, 2015 at 1:01 PM, Richard Smith <richard at metafoo.co.uk>
wrote:

> On Mon, Jan 12, 2015 at 1:26 AM, David Chisnall <
> David.Chisnall at cl.cam.ac.uk> wrote:
>
>> On 12 Jan 2015, at 08:07, Dimitry Andric <dimitry at andric.com> wrote:
>> >
>> >
>> > On 15 Oct 2014, at 19:42, Richard Smith <richard at metafoo.co.uk> wrote:
>> >> On 15 Oct 2014 05:12, "Ed Schouten" <ed at 80386.nl> wrote:
>> > ...
>> >> The test case in the LLVM tree is invalid and should be discarded. It
>> >> erroneously assumes that the encoding of wchar_t is independent of the
>> >> locale.
>> >>
>> > That makes no sense. These value are compile-time constants and cannot
>> possibly depend on the locale.
>>
>> I believe Richard is wrong here.  There are a number of similar
>> compile-time constant macros in the C spec.  I believe the clue as to the
>> correct reading of the spec is in the name of the macro:
>> __STDC_MB_MIGHT_NEQ_WC__
>>
>> Note the word *might*.  It means that it is not safe for code to assume
>> that a cast will give the corresponding char value if one exists.  i.e.
>> that assumption is not true for all locales.
>>
>
> You should read the definitions in the relevant standards rather than
> trying to guess what the macro means from its name. Here is the definition:
>
> "The integer constant 1, intended to indicate that, in the encoding for
> wchar_t, a member of the basic character set need not have a code value
> equal to its value when used as the lone character in an integer character
> constant."
>
> So the value 1 indicates that 'x' might not equal L'x' for some character
> x in the basic character set. (Note that the 'might' means that there might
> exist some *character* where this happens, not that there might exist some
> *locale* where this happens.) Since the value of 'x' and L'x' are
> determined at translation time, this property obviously cannot depend in
> any way on the current locale in the execution environment.
>
> Note that the above property is *exactly* what the test is testing for.
>
> However... the FreeBSD folks don't seem interested in fixing their bug,
> and it's technically conforming for an implementation to define this macro
> to 1 in any situation -- a member of the basic source character set "need
> not" have the same value as a narrow or wide character, even though they
> all actually do -- making this a quality-of-implementation issue, and I'm
> tired of discussing this, so I've relaxed the test for FreeBSD in r225751.
>
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>
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