c++ map/set iterator 不可解引用 --- map<const char *, string>

Question

class A
{
public:
    map<string, string> strs; // it's initialized in a function
    map<const char *, string> myMap;
    virtual void setMyMap()
    {
        myMap.insert({str.begin()->first.c_str(), "aaa"});
    }
};

class B : public class A
{};

class C : public class B
{
    virtual void setMyMap()
    {
        B::setMyMap();
        for (auto it = myMap.begin(); it != myMap.end(); ++it)
        {
            cout << it->first << std::endl; // "a"
        }
        cout<<(myMap.find("a") == myMap.end()); // 1
        myMap.find("a")->first; // get the error
    }
};

Here is my code.
I get the error map/set iterator not dereferencable in the function setMyMap in the class C .
I get this error because myMap.find("a") == myMap.end() is true .
But I don't know why. To my surprise, I just print this map in the same function and I can see all of the first of this map. Here I can see a . I really don't know why I try to find the same first but failed. a is definitely in the map. Otherwise I can't print it with that for .

Answer 1

A map with const char * as they key does NOT compare the strings, only the pointer addresses. Two strings "a" at different addresses will not compare equal. You must use std::string or a custom compare function. Do not make assumptions about the addresses of string literals.