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<p>I know that g++ support constexpr math function. I want to do that on clang++. So I write a simple code.</p>
<pre><code>#include<iostream>
#include<cmath>
int main()
{
constexpr auto a(std::floor(4.3));
std::cout<<a<<std::endl;
}
</code></pre>
<p>and then use clang++-libc++ -std=c++1y to compile it and the get the following error:</p>
<pre><code>error: constexpr variable 'a' must be initialized by a constant expression
constexpr auto a(std::floor(4.3));
^ ~~~~~~~~~~~~~~~
note: non-constexpr function 'floor' cannot be used in a constant expression
constexpr auto a(std::floor(4.3));
^
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:184:14: note: declared here
__MATHCALLX (floor,, (_Mdouble_ __x), (__const__));
^
/usr/include/math.h:58:26: note: expanded from macro '__MATHCALLX'
__MATHDECLX (_Mdouble_,function,suffix, args, attrib)
^
/usr/include/math.h:60:22: note: expanded from macro '__MATHDECLX'
__MATHDECL_1(type, function,suffix, args) __attribute__ (attrib); \
^
/usr/include/math.h:63:31: note: expanded from macro '__MATHDECL_1'
extern type __MATH_PRECNAME(function,suffix) args __THROW
^
/usr/include/math.h:66:42: note: expanded from macro '__MATH_PRECNAME'
#define __MATH_PRECNAME(name,r) __CONCAT(name,r)
^
/usr/include/x86_64-linux-gnu/sys/cdefs.h:88:23: note: expanded from macro '__CONCAT'
#define __CONCAT(x,y) x ## y
</code></pre>
<p>I use clang-3.5. So I want to ask whether clang++ support constexpr math function. If so, what compiler flag I need to pass to clang?</p>
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