c++ allocating and deallocating dynamical array of objects

Question

I'm a little bit confused on how to correctly allocate/deallocate dynamical array of objects. Here is my scenario:

class Tuple { public: Tuple(int columns); ~Tuple(); void set(int i, string d); string get(int i); int columnCount(); private: string *data; int columns; }; Tuple::Tuple(int columns) { this->columns = columns > 0 ? columns : 0; if (this->columns > 0) { data = new string[this->columns]; } else { data = 0; } } Tuple::~Tuple() { if (columns > 0) { delete data; } }

Now, when I call the following code I get a segfault:

Tuple *t = new Tuple(4); //some code delete t;

What is wrong with my denstructor?

bobah · Accepted Answer · 2013-12-09 20:26:55Z

4

You need to use array delete operator in your destructor:

delete [] data;

The destructor can be written as

Tuple::~Tuple() { delete [] data; }

answered Dec 9, 2013 at 20:26

bobah

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2 Comments

bobah Over a year ago

@Dan do not judge and you won't be judged

bobah Over a year ago

@LightnessRacesinOrbit - there are reproducible facts and there are false confidence and baseless speculations

Lightness Races in Orbit · Accepted Answer · 2013-12-09 20:30:15Z

2

What is wrong with my denstructor?

You wrote delete instead of delete[].

BTW you're also missing a copy constructor and assignment operator, so your class is more subtly broken and rather susceptible to memory leaks.

how to correctly allocate/deallocate dynamical array of objects.

Don't.

Use a std::vector<std::string>.

answered Dec 9, 2013 at 20:30

Lightness Races in Orbit

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3 Comments

Lightness Races in Orbit Over a year ago

@the_candyman: Why use a vector? So that its allocation and de-allocation is managed for you and you don't need to worry about any of this (including the three bugs in your attempt). In case you were wondering, there is no downside.

the_candyman Over a year ago

ok, but what if I want to allocate exactly a certain amount of memory?

Lightness Races in Orbit Over a year ago

@the_candyman: Then ask the vector to do that. Read the chapter about vectors in your C++ book. They're really easy to use: way easier than this manual memory management gubbins.

Lightness Races in Orbit · Accepted Answer · 2013-12-09 20:35:44Z

I encourage you to look up the difference between:

delete
delete (nothrow_t)
delete []
delete [] (nothrow_t)

and look into their new equivalents, and when one should be used over the other.

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