珍爱生命远离c++就是这么来的
1.#include"stdio.h"
2.#include"sparsepp-master/sparsepp.h"
3.int main()
4.{
5. spp::sparse_hash_map<std::pair<int,int>,int> mp;
6.mp.insert(std::make_pair(std::make_pair(1,1),1));
7.return 0;
8.}
这个程序时使用sparsepp库提供的hash版map来存数据的例子，但他有一个错误：库中并没有给出为std::pair<int,int>产生hash值的算法，因此该程序不能工作。
理想情况下我们想要编译器这么提示我们：“亲爱的程序员，您的程序这里有错，错误原因和解决方法我都给你标注好了，么么嗒~~~”
具体错误提示大概长这样：
line 6:mp.insert(std::make_pair(std::make_pair(1,1),1));
^^^^^^^^^^^^^^^^^^^ can't generate serialization
但实际上有点困难，一般编译器只会这么提示我们：“吔屎啦，这里这里这里这里这里这里我都看不懂，赶紧给老娘改！”
JAVA和javascript就喜欢这么干，错误提示大概长这样：
In file sparsepp-master/sparsepp.h:1483:42: XXXXXX
In file sparsepp-master/sparsepp.h:5069:77: XXXXXX
In file main.cpp:6:25: type cast failed
In file main.cpp:3:1: XXXXX
而混乱邪恶的C++是这样提示我们的：
In file included from main.cpp:2:0:
sparsepp-master/sparsepp.h: In instantiation of 'size_t spp::spp_hash<T>::operator()(const T&) const [with T = std::pair<int, int>; size_t = long long unsigned int]':
sparsepp-master/sparsepp.h:1483:42: required from 'size_t spp::sparsehash_internal::sh_hashtable_settings<Key, HashFunc, SizeType, HT_MIN_BUCKETS>::hash(const key_type&) const [with Key = std::pair<int, int>; HashFunc = spp::spp_hash<std::pair<int, int> >; SizeType = long long unsigned int; int HT_MIN_BUCKETS = 4; size_t = long long unsigned int; spp::sparsehash_internal::sh_hashtable_settings<Key, HashFunc, SizeType, HT_MIN_BUCKETS>::key_type = std::pair<int, int>]'
sparsepp-master/sparsepp.h:4729:31: required from 'size_t spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::hash(const key_type&) const [with Value = std::pair<std::pair<int, int>, int>; Key = std::pair<int, int>; HashFcn = spp::spp_hash<std::pair<int, int> >; ExtractKey = spp::sparse_hash_map<std::pair<int, int>, int>::SelectKey; SetKey = spp::sparse_hash_map<std::pair<int, int>, int>::SetKey; EqualKey = std::equal_to<std::pair<int, int> >; Alloc = spp::libc_allocator_with_realloc<std::pair<const std::pair<int, int>, int> >; size_t = long long unsigned int; spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::key_type = std::pair<int, int>]'
sparsepp-master/sparsepp.h:4242:33: required from 'spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::Position spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::_find_position(const key_type&) const [with Value = std::pair<std::pair<int, int>, int>; Key = std::pair<int, int>; HashFcn = spp::spp_hash<std::pair<int, int> >; ExtractKey = spp::sparse_hash_map<std::pair<int, int>, int>::SelectKey; SetKey = spp::sparse_hash_map<std::pair<int, int>, int>::SetKey; EqualKey = std::equal_to<std::pair<int, int> >; Alloc = spp::libc_allocator_with_realloc<std::pair<const std::pair<int, int>, int> >; spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::key_type = std::pair<int, int>]'
sparsepp-master/sparsepp.h:4401:38: required from 'std::pair<typename spp::sparsetable<Value, typename Alloc::rebind<Value>::other>::ne_iterator, bool> spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::_insert_noresize(T&) [with T = const std::pair<const std::pair<int, int>, int>; Value = std::pair<std::pair<int, int>, int>; Key = std::pair<int, int>; HashFcn = spp::spp_hash<std::pair<int, int> >; ExtractKey = spp::sparse_hash_map<std::pair<int, int>, int>::SelectKey; SetKey = spp::sparse_hash_map<std::pair<int, int>, int>::SetKey; EqualKey = std::equal_to<std::pair<int, int> >; Alloc = spp::libc_allocator_with_realloc<std::pair<const std::pair<int, int>, int> >; typename spp::sparsetable<Value, typename Alloc::rebind<Value>::other>::ne_iterator = spp::Two_d_iterator<std::pair<std::pair<int, int>, int>, spp::sparsegroup<std::pair<std::pair<int, int>, int>, spp::libc_allocator_with_realloc<std::pair<std::pair<int, int>, int> > >*, std::pair<const std::pair<int, int>, int>*, std::bidirectional_iterator_tag>]'
sparsepp-master/sparsepp.h:4451:36: required from 'std::pair<typename spp::sparsetable<Value, typename Alloc::rebind<Value>::other>::ne_iterator, bool> spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::insert(spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::const_reference) [with Value = std::pair<std::pair<int, int>, int>; Key = std::pair<int, int>; HashFcn = spp::spp_hash<std::pair<int, int> >; ExtractKey = spp::sparse_hash_map<std::pair<int, int>, int>::SelectKey; SetKey = spp::sparse_hash_map<std::pair<int, int>, int>::SetKey; EqualKey = std::equal_to<std::pair<int, int> >; Alloc = spp::libc_allocator_with_realloc<std::pair<const std::pair<int, int>, int> >; typename spp::sparsetable<Value, typename Alloc::rebind<Value>::other>::ne_iterator = spp::Two_d_iterator<std::pair<std::pair<int, int>, int>, spp::sparsegroup<std::pair<std::pair<int, int>, int>, spp::libc_allocator_with_realloc<std::pair<std::pair<int, int>, int> > >*, std::pair<const std::pair<int, int>, int>*, std::bidirectional_iterator_tag>; spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::const_reference = const std::pair<const std::pair<int, int>, int>&; spp::sparse_hashtable<Value, Key, HashFcn, ExtractKey, SetKey, EqualKey, Alloc>::value_type = std::pair<const std::pair<int, int>, int>]'
sparsepp-master/sparsepp.h:5069:77: required from 'std::pair<typename spp::sparse_hashtable<std::pair<typename spp::remove_const<Key>::type, T>, Key, HashFcn, spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::SelectKey, spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::SetKey, EqualKey, Alloc>::iterator, bool> spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::insert(const value_type&) [with Key = std::pair<int, int>; T = int; HashFcn = spp::spp_hash<std::pair<int, int> >; EqualKey = std::equal_to<std::pair<int, int> >; Alloc = spp::libc_allocator_with_realloc<std::pair<const std::pair<int, int>, int> >; typename spp::sparse_hashtable<std::pair<typename spp::remove_const<Key>::type, T>, Key, HashFcn, spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::SelectKey, spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::SetKey, EqualKey, Alloc>::iterator = spp::Two_d_iterator<std::pair<std::pair<int, int>, int>, spp::sparsegroup<std::pair<std::pair<int, int>, int>, spp::libc_allocator_with_realloc<std::pair<std::pair<int, int>, int> > >*, std::pair<const std::pair<int, int>, int>*, std::bidirectional_iterator_tag>; spp::sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>::value_type = std::pair<const std::pair<int, int>, int>]'
main.cpp:6:49: required from here
sparsepp-master/sparsepp.h:943:27: error: use of deleted function 'std::hash<std::pair<int, int> >::hash()'
SPP_HASH_CLASS<T> hasher;
^~~~~~
In file included from E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/basic_string.h:5628:0,
from E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/string:52,
from sparsepp-master/sparsepp.h:839,
from main.cpp:2:
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:85:12: note: 'std::hash<std::pair<int, int> >::hash()' is implicitly deleted because the default definition would be ill-formed:
struct hash : __hash_enum<_Tp>
^~~~
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:85:12: error: no matching function for call to 'std::__hash_enum<std::pair<int, int>, false>::__hash_enum()'
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:66:7: note: candidate: std::__hash_enum<_Tp, <anonymous> >::__hash_enum(std::__hash_enum<_Tp, <anonymous> >&&) [with _Tp = std::pair<int, int>; bool <anonymous> = false]
__hash_enum(__hash_enum&&);
^~~~~~~~~~~
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:66:7: note: candidate expects 1 argument, 0 provided
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:85:12: error: 'std::__hash_enum<_Tp, <anonymous> >::~__hash_enum() [with _Tp = std::pair<int, int>; bool <anonymous> = false]' is private within this context
struct hash : __hash_enum<_Tp>
^~~~
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:67:7: note: declared private here
~__hash_enum();
^
In file included from main.cpp:2:0:
sparsepp-master/sparsepp.h:943:27: error: use of deleted function 'std::hash<std::pair<int, int> >::~hash()'
SPP_HASH_CLASS<T> hasher;
^~~~~~
In file included from E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/basic_string.h:5628:0,
from E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/string:52,
from sparsepp-master/sparsepp.h:839,
from main.cpp:2:
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:85:12: note: 'std::hash<std::pair<int, int> >::~hash()' is implicitly deleted because the default definition would be ill-formed:
struct hash : __hash_enum<_Tp>
^~~~
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:85:12: error: 'std::__hash_enum<_Tp, <anonymous> >::~__hash_enum() [with _Tp = std::pair<int, int>; bool <anonymous> = false]' is private within this context
E:/mingw-w64/x86_64-6.3.0-posix-seh-rt_v5-rev2/mingw64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/functional_hash.h:67:7: note: declared private here
~__hash_enum();
^
In file included from main.cpp:2:0:
sparsepp-master/sparsepp.h:944:22: error: no match for call to '(std::hash<std::pair<int, int> >) (const std::pair<int, int>&)'
return hasher(__v);
~~~~~~^~~~~
☻☺这只是一段代码报错时候弹出的提示，当你想像一下一句话报错就能出现这么长的代码，当一个程序出现问题的时候，你找个错误都得找半天，所以大部分人都会选择修复bug然后就出现了更多的bug。
