迭代器，導致seg錯誤的循環！爲什麼它循環太多？

Question

下面的代碼會經歷循環太多次，而我爲什麼會感到困惑。我環顧四周，並沒有看到像這樣的案例。我對迭代器相當陌生，所以這裏可能有些簡單。感謝您的幫助！希望對未來的其他人有所幫助。

std::multimap<std::string,std::vector<Token> >::iterator end = theFacts.returnContents().end(); 
for (mapITER = theFacts.returnContents().begin() ; mapITER != end; mapITER++) { 

    cout << "ANOTHER ITERATION THROUGH FACTS" << endl; 
    cout << mapITER->first << endl; 
    cout << contents.begin()->first << endl; 

    if (mapITER->first == contents.begin()->first) { 

    cout << "same scheem type so I keep going!" << endl; 

    bool successfull = true; 

    cout << "starting to seek match --> size --> " << mapITER->second.size() << endl; 

    for (int x = 0; x< mapITER->second.size(); x++) { 

     std::cout << "processing! " 
       << mapITER->second[x].getTokensValue() << "<<<<<<is equal?>>>>>>" 
       << contents.begin()->second[x].getTokensValue() << std::endl; 

     if (mapITER->second[x].getTokensValue() 
     == contents.begin()->second[x].getTokensValue()) { 

     cout << "pushing value" << endl; 
     newBaby.push_back(contents.begin()->second[x]); 

     } else { 

     cout << "failure" << endl; 
     successfull = false; 
     } 
    } 

    if (successfull) { 

     std::cout << "match successfully found" << std::endl; 

     if (returnme.contents.empty()) { 

     returnme = Relation(contents.begin()->first, newBaby); 
     cout << returnme.toString() << endl; 

     } else { 

     returnme.relationInsert(contents.begin()->first, newBaby); 
     cout << returnme.toString() << endl; 
     } 

    } else { 
     // Anser is NO 
    } 
    } 
} 

我知道我不能提供完整的代碼，但你可以看到形成了下面的輸出，我通過遍歷地圖的大小爲2，那麼爲什麼它循環第三次！

WHERE TO END --> size of maps (number of iterations that shoudl occure2 
ANOTHER ITERATION THROUGH FACTS 
snap 
snap 
same scheem type so I keep going! 
starting to seek match --> size --> 4 
processing! '12345'<<<<<<is equal?>>>>>>'67890' 
failure 
processing! 'Snoopy'<<<<<<is equal?>>>>>>'Van Pelt' 
failure 
processing! '12 Apple'<<<<<<is equal?>>>>>>'34 Pear' 
failure 
processing! '555-1234'<<<<<<is equal?>>>>>>'555-5678' 
failure 
ANOTHER ITERATION THROUGH FACTS 
snap 
snap 
same scheem type so I keep going! 
starting to seek match --> size --> 4 
processing! '67890'<<<<<<is equal?>>>>>>'67890' 
pushing value 
processing! 'Van Pelt'<<<<<<is equal?>>>>>>'Van Pelt' 
pushing value 
processing! '34 Pear'<<<<<<is equal?>>>>>>'34 Pear' 
pushing value 
processing! '555-5678'<<<<<<is equal?>>>>>>'555-5678' 
pushing value 
match successfully found 
PRINT RELATION CALLED 
snap('67890','Van Pelt','34 Pear','555-5678') 
ANOTHER ITERATION THROUGH FACTS 
Segmentation fault (core dumped) 

這裏是返回內容的作用。

std::multimap<std::string,std::vector<Token> > Relation :: returnContents() 
{ 
    return contents; 
} 

其中內容是Relation類中的私有變量。在我看來，這不應該導致錯誤，除非有什麼明顯的我不知道。

Answer 1

這裏是返回內容的作用。

在那裏你有你的錯誤。函數returnContents返回地圖的副本。然後，您可以撥打begin和end兩個副本。

要麼返回一個（常量）參考：

const std::multimap<std::string,std::vector<Token> >& Relation::returnContents() { 
    return contents; 
} 

，或者創建一個本地副本：

std::multimap<std::string,std::vector<Token> > tmp = theFacts.returnContents(); 
for (mapITER = tmp.begin() ; mapITER != tmp.end(); mapITER++) { ...