Cygwin的gcc.4.9.2：错误： ':: lrintl' 尚未声明

问题描述：

这一问题与此主题：cygwin support for C++11 in g++4.9.2 Cygwin的gcc.4.9.2：错误： ':: lrintl' 尚未声明

我有同样的问题：

error: ‘log2’ is not a member of ‘std’

我申请建议的补丁，只能得到另一个错误。这里包括CMATH

#include <cmath> 
#include <iostream> 
int main() 
{ 
     std::cout << "hello" << std::endl; 
}

返回该错误

$ g++ -std=c++11 test.cpp 
In file included from test.cpp:1:0: 
/usr/lib/gcc/x86_64-pc-cygwin/4.9.2/include/c++/cmath:1107:11: error: '::lrintl' has not been declared 
    using ::lrintl; 
     ^
/usr/lib/gcc/x86_64-pc-cygwin/4.9.2/include/c++/cmath:1129:11: error: '::rintl' has not been declared 
    using ::rintl;

我要求在cygwin的IRC频道求助：

[23:02] <XXX> hi, has anyone had problems with gcc 4.9.2 in cygwin? i encountered the problem discussed here : https://cygwin.com/ml/cygwin/2015-03/msg00247.html 
[23:03] <XXX> yet, if i apply the patch, i get another error: /usr/lib/gcc/x86_64-pc-cygwin/4.9.2/include/c++/cmath:1107:11: error: '::lrintl' has not been declared 
[23:28] <YYY> long double functions are still missing on cygwin 
[23:30] <XXX> so is there no way to make it work then? 
[23:31] <YYY> sure, help add the missing functions to newlib/cygwin 
[23:34] <XXX> i am not using any long double functions in my code -- so i assume including cmath does not work for anybody? 
[23:35] <YYY> just drop the std:: instead 
[23:37] <XXX> sorry, i'm not sure what you mean. remove 'std::' where ?

可悲的是，谈话结束那里。我不知道应该在哪里放下std ::'，也不能解决问题。任何人都可以帮忙吗？

由于提前，贡纳尔

答

未打补丁的<cmath>工作正常，在这里，如果我做的：的

auto x = log2(10);

代替：

auto x = std::log2(10);

也许这就是YYY是指“下降STD ::”。

如果必须使用修补<cmath>，您可以注释掉两行违规，或者如果你不想修改头的任何比你已经有了，加rintl和lrintl一些虚拟的定义，你包括前它。例如：

#include <stdexcept> 
long double rintl(long double arg) { throw std::runtime_error("rintl not implemented"); } 
long lrintl(long double arg) { throw std::runtime_error("lrintl not implemented"); } 

#include <cmath>

Cygwin的gcc.4.9.2：错误： ':: lrintl' 尚未声明

相关推荐