[cfe-dev] Looks lie a bug: no implicit conversion from slice_array to valarray in 3.4.1 + libcpp

[Marshall Clow]

On Sep 15, 2014, at 9:48 AM, Lev Serebryakov <lev at FreeBSD.org> wrote:

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> On 15.09.2014 20:38, Marshall Clow wrote:
> 
>>> I'm using clang 3.4.1 (FreeBSD-CURRENT system compiler) with I'm
>>> compile very simple program, which uses <valarray>. Of course, it
>>> is test case, I found this bug when try to compile qucs project
>>> on this system ============ test.cpp #include <valarray>
>>> 
>>> int main(int argc, char *argv[]) { std::valarray<double> a(4,
>>> 10); std::valarray<double> b(4, 20); a *= b[std::slice(1,1,1)]; 
>>> return 0; } =====================
>> 
>> I’ve opened issue http://llvm.org/bugs/show_bug.cgi?id=20946 to
>> track this.
>> 
>> I’m not sure if this is a bug in libc++, or an extension in
>> libstdc++. A quick look at the standard doesn’t show any implicit
>> conversions from a single-element slice array (the result of
>> 'b[std::slice(1,1,1)]’) to a double.
>> 
>> Thanks for the report.
> I could be wrong (I'm not C++ guru), but looks like
> slice_array<double> should be converted to valarray<double> in such
> case with appropriate valarray's constructor (it isn't marked as
> "explicit"), because there are appropriate "operator *=" in valarray
> class to multiple two valarrays.

Yes, that seems to be the case.
You’re welcome to add yourself to the bug, and then you’ll get notifications 
as it is updated.

> I want to note, that in real code I encounter this, slice was not
> single-element, and it worked in gcc 4.8. Maybe, my trimmed example is
> not very good (due to single-element slice, which could lead to
> confusion).
> 

Right. Noted.
Thanks again.

— Marshall

> - -- 
> // Lev Serebryakov
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