编译be出错，重复定义struct std::hash<__int128>

[crcc]

编译be时报错

In file included from /home/crc/palo/be/src/runtime/decimal_value.h:34:0,
from /home/crc/palo/be/src/udf/udf.cpp:27:
/home/crc/palo/be/src/util/hash_util.hpp:303:8: error: redefinition of ‘struct std::hash<__int128>’
struct hash<__int128> {
^~~~~~~~~~~~~~
In file included from /usr/include/c++/6/bits/basic_string.h:5643:0,
from /usr/include/c++/6/string:52,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from /home/crc/palo/be/src/udf/udf.cpp:23:
/usr/include/c++/6/bits/functional_hash.h:153:3: error: previous definition of ‘struct std::hash<__int128>’
_Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0)
^

我使用的是debian stretch（当前的stable版本），gcc version 6.3.0 20170516 (Debian 6.3.0-18)
gcc -print-prog-name=cc1plus -v的结果如下
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/6/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/6
/usr/include/x86_64-linux-gnu/c++/6
/usr/include/c++/6/backward
/usr/lib/gcc/x86_64-linux-gnu/6/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/6/include-fixed
/usr/include
End of search list.

手动把be/CMakeLists.txt中的CLANG_BASE_FLAGS设置如下
set(CLANG_BASE_FLAGS
"-I/usr/include/c++/6/"
"-I/usr/include/x86_64-linux-gnu/c++/6")

[imay]

看样子应该是GCC6支持了struct hash<__int128>，应该可以通过宏定义来把hash包起来
欢迎提PR。

[crcc]

c++不熟，不知道hash用在哪里

g++ 定义的hash如下，只是简单的cast
// Explicit specializations for integer types.
#define _Cxx_hashtable_define_trivial_hash(_Tp)
template<>
struct hash<_Tp> : public __hash_base<size_t, _Tp>
{
size_t
operator()(_Tp __val) const noexcept
{ return static_cast<size_t>(__val); }
};

用这个靠谱吗？还是要用你们定义的？

[imay]

这个hash函数用在了std::unordered_map中，如果你没法提交的话，可以简单注释掉我们自己实现的hash看看能否编译通过

[morningman]

Not a problem anymore, using docker dev environment instead