赛格。 在std :: vector上推送指针时出错

Question

I have profiled the following code with Valgrind and got the following:

Use of uninitialised value of size 8
invalid read of size 8

when executing this line:

compuMethod->keywordlist->push_back(keyword);

However, I have clearly initialized keyword ...

#include <iostream>
#include <vector>
#include <map>
#include <string>
using namespace std;

class Keyword;
class CompuMethod;

typedef std::vector<Keyword*> KeywordList;
std::map<std::string, CompuMethod*> AllCompuMethods;

class Keyword
{
    private:
        std::string _name;

    public:
        Keyword(std::string name) : _name(name) {}
        virtual ~Keyword() {}
        std::string GetName() { return(_name); }
};

class CompuMethod
{
    public:
        CompuMethod(){}
        ~CompuMethod(){}
        KeywordList* keywordlist;

};

int main()
{
    CompuMethod* compuMethod = new CompuMethod();
    Keyword* keyword = new Keyword("terminal");
    compuMethod->keywordlist->push_back(keyword);

    //Call delete for each new
    return 0;
}

I am obviously overlooking something. What am I doing on this line:

Keyword* keyword = new Keyword("terminal");

that is NOT initializing keyword ?

Answer 1

keyword is initialised correctly. The problem is that you didn't allocate compuMethod->keywordlist

You should either make keywordlist a KeywordList rather than a pointer or allocate it in CompuMethod() (deleting it in the destructor)

Answer 2

keywordlist is a pointer to std::vector<Keyword*>

You can't simply push items into it.

Use following to allocate memory for the pointer to vector in the Constructor

CompuMethod(){keywordlist = new KeywordList();}

And accordingly update the Destructor

~CompuMethod(){ delete keywordlist; }

Edit :

greyfade comment -

" But don't forget the copy/move ctor and operator= to properly handle the pointer. Otherwise, you'll end up with double-frees "