是否有一种方法可以让gcc/g++从命令行转储其默认的预处理器定义? 我的意思是像__GNUC__, __STDC__,等等。
是否有一种方法可以让gcc/g++从命令行转储其默认的预处理器定义? 我的意思是像__GNUC__, __STDC__,等等。
我试图使用一个自定义类作为unordered_map的键,如下所示:
#include <iostream>
#include <algorithm>
#include <unordered_map>
using namespace std;
class node;
class Solution;
class Node {
public:
int a;
int b;
int c;
Node(){}
Node(vector<int> v) {
sort(v.begin(), v.end());
a = v[0];
b = v[1];
c = v[2];
}
bool operator==(Node i) {
if ( i.a==this->a && i.b==this->b &&i.c==this->c ) {
return true;
} else {
return false;
}
}
};
int main() {
unordered_map<Node, int> m;
vector<int> v;
v.push_back(3);
v.push_back(8);
v.push_back(9);
Node n(v);
m[n] = 0;
return 0;
}
然而,g++给出了以下错误:
In file included from /usr/include/c++/4.6/string:50:0,
from /usr/include/c++/4.6/bits/locale_classes.h:42,
from /usr/include/c++/4.6/bits/ios_base.h:43,
from /usr/include/c++/4.6/ios:43,
from /usr/include/c++/4.6/ostream:40,
from /usr/include/c++/4.6/iostream:40,
from 3sum.cpp:4:
/usr/include/c++/4.6/bits/stl_function.h: In member function ‘bool std::equal_to<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = Node]’:
/usr/include/c++/4.6/bits/hashtable_policy.h:768:48: instantiated from ‘bool std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2, std::__detail::_Default_ranged_hash, false>::_M_compare(const _Key&, std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2, std::__detail::_Default_ranged_hash, false>::_Hash_code_type, std::__detail::_Hash_node<_Value, false>*) const [with _Key = Node, _Value = std::pair<const Node, int>, _ExtractKey = std::_Select1st<std::pair<const Node, int> >, _Equal = std::equal_to<Node>, _H1 = std::hash<Node>, _H2 = std::__detail::_Mod_range_hashing, std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2, std::__detail::_Default_ranged_hash, false>::_Hash_code_type = long unsigned int]’
/usr/include/c++/4.6/bits/hashtable.h:897:2: instantiated from ‘std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_Node* std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_M_find_node(std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_Node*, const key_type&, typename std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_Hash_code_type) const [with _Key = Node, _Value = std::pair<const Node, int>, _Allocator = std::allocator<std::pair<const Node, int> >, _ExtractKey = std::_Select1st<std::pair<const Node, int> >, _Equal = std::equal_to<Node>, _H1 = std::hash<Node>, _H2 = std::__detail::_Mod_range_hashing, _Hash = std::__detail::_Default_ranged_hash, _RehashPolicy = std::__detail::_Prime_rehash_policy, bool __cache_hash_code = false, bool __constant_iterators = false, bool __unique_keys = true, std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_Node = std::__detail::_Hash_node<std::pair<const Node, int>, false>, std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::key_type = Node, typename std::_Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal, _H1, _H2, _Hash, _RehashPolicy, __cache_hash_code, __constant_iterators, __unique_keys>::_Hash_code_type = long unsigned int]’
/usr/include/c++/4.6/bits/hashtable_policy.h:546:53: instantiated from ‘std::__detail::_Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::mapped_type& std::__detail::_Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::operator[](const _Key&) [with _Key = Node, _Pair = std::pair<const Node, int>, _Hashtable = std::_Hashtable<Node, std::pair<const Node, int>, std::allocator<std::pair<const Node, int> >, std::_Select1st<std::pair<const Node, int> >, std::equal_to<Node>, std::hash<Node>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, false, false, true>, std::__detail::_Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::mapped_type = int]’
3sum.cpp:149:5: instantiated from here
/usr/include/c++/4.6/bits/stl_function.h:209:23: error: passing ‘const Node’ as ‘this’ argument of ‘bool Node::operator==(Node)’ discards qualifiers [-fpermissive]
make: *** [threeSum] Error 1
我想,我需要告诉c++如何哈希类节点,然而,我不太确定如何做到这一点。我怎样才能完成这个任务呢?
我试图更新我的c++编译器到c++ 11。 我已经搜索了一点,我得出的结论是,我必须使用标志-std=c++0x或-std=gnu++0x,但我不知道很多关于标志的事情。有人能帮帮我吗?(我使用的是Ubuntu 12.04。)
以下是我试图使用c++ 11中包含的库(即数组)时从编译器得到的错误:
#include <array>
#include <iostream>
int main()
{
std::array<int, 3> arr = {2, 3, 5};
...
}
该文件需要即将发布的ISO c++标准c++ 0x的编译器和库支持。这种支持目前是实验性的,必须使用-std=c++0x或-std=gnu++0x编译器选项来启用。
当构建我的c++程序时,我得到了错误消息
未定义的引用'vtable…
这个问题的原因是什么?我该怎么解决呢?
碰巧,我得到以下代码的错误(类的问题是CGameModule.),我不能为我的生活理解问题是什么。起初,我认为这与忘记给虚拟函数赋予一个主体有关,但据我所知,一切都在这里。继承链有点长,但这里有相关的源代码。我不确定我还需要提供什么信息。
注意:这个错误似乎发生在构造函数中。
我的代码:
class CGameModule : public CDasherModule {
public:
CGameModule(Dasher::CEventHandler *pEventHandler, CSettingsStore *pSettingsStore, CDasherInterfaceBase *pInterface, ModuleID_t iID, const char *szName)
: CDasherModule(pEventHandler, pSettingsStore, iID, 0, szName)
{
g_pLogger->Log("Inside game module constructor");
m_pInterface = pInterface;
}
virtual ~CGameModule() {};
std::string GetTypedTarget();
std::string GetUntypedTarget();
bool DecorateView(CDasherView *pView) {
//g_pLogger->Log("Decorating the view");
return false;
}
void SetDasherModel(CDasherModel *pModel) { m_pModel = pModel; }
virtual void HandleEvent(Dasher::CEvent *pEvent);
private:
CDasherNode *pLastTypedNode;
CDasherNode *pNextTargetNode;
std::string m_sTargetString;
size_t m_stCurrentStringPos;
CDasherModel *m_pModel;
CDasherInterfaceBase *m_pInterface;
};
继承自…
class CDasherModule;
typedef std::vector<CDasherModule*>::size_type ModuleID_t;
/// \ingroup Core
/// @{
class CDasherModule : public Dasher::CDasherComponent {
public:
CDasherModule(Dasher::CEventHandler * pEventHandler, CSettingsStore * pSettingsStore, ModuleID_t iID, int iType, const char *szName);
virtual ModuleID_t GetID();
virtual void SetID(ModuleID_t);
virtual int GetType();
virtual const char *GetName();
virtual bool GetSettings(SModuleSettings **pSettings, int *iCount) {
return false;
};
private:
ModuleID_t m_iID;
int m_iType;
const char *m_szName;
};
哪个继承自....
namespace Dasher {
class CEvent;
class CEventHandler;
class CDasherComponent;
};
/// \ingroup Core
/// @{
class Dasher::CDasherComponent {
public:
CDasherComponent(Dasher::CEventHandler* pEventHandler, CSettingsStore* pSettingsStore);
virtual ~CDasherComponent();
void InsertEvent(Dasher::CEvent * pEvent);
virtual void HandleEvent(Dasher::CEvent * pEvent) {};
bool GetBoolParameter(int iParameter) const;
void SetBoolParameter(int iParameter, bool bValue) const;
long GetLongParameter(int iParameter) const;
void SetLongParameter(int iParameter, long lValue) const;
std::string GetStringParameter(int iParameter) const;
void SetStringParameter(int iParameter, const std::string & sValue) const;
ParameterType GetParameterType(int iParameter) const;
std::string GetParameterName(int iParameter) const;
protected:
Dasher::CEventHandler *m_pEventHandler;
CSettingsStore *m_pSettingsStore;
};
/// @}
#endif
我试图编译我的程序,它返回这个错误:
usr/bin/ld: cannot find -l<nameOfTheLibrary>
在我的makefile中,我使用命令g++并链接到我的库,这是一个符号链接到我的库位于另一个目录。
是否有一个选项添加,使其工作,请?
g++和gcc的区别是什么?它们中的哪一个应该用于一般的c++开发?