How to free memory allocated by a vector of string?

[Piotr]

If I have a vector of string, is a call to 'empty()' sufficient to free
the all memory (i.e. no memory leaks)?

vector <string> str_vector;
str_vector.push_back("hello");
str_vector.push_back("world");

str_vector.empty();

And what if i have a vector of string pointer.
vecto <string*> str_vector;
string* str1= new string();
string* str2= new string();

str_vector.push_back(str1);
str_vector.push_back(str1);

str_vector.empty();

 

[Sharad Kala]

| If I have a vector of string, is a call to 'empty()' sufficient to free
| the all memory (i.e. no memory leaks)?

You don't need to bother about memory management with vector. It takes care
of allocation and deallocation on its own.

| vector <string> str_vector;
| str_vector.push_back("hello");
| str_vector.push_back("world");
|
| str_vector.empty();

Not required.

| And what if i have a vector of string pointer.
| vecto <string*> str_vector;
| string* str1= new string();
| string* str2= new string();

Of course you need to free str1 and str2 on your own. Simple rule is that
you need to delete as many times as you have invoked new.

| str_vector.push_back(str1);
| str_vector.push_back(str1);

Sharad

 

[Kai-Uwe Bux]

If I have a vector of string, is a call to 'empty()' sufficient to free
the all memory (i.e. no memory leaks)?

vector <string> str_vector;
str_vector.push_back("hello");
str_vector.push_back("world");

str_vector.empty();

This empties the vector and destroys all string objects therein. Upon their
destruction, each of these string objects takes care of its own memory.
There are no leaks.

And what if i have a vector of string pointer.
vecto <string*> str_vector;
string* str1= new string();
string* str2= new string();

str_vector.push_back(str1);
str_vector.push_back(str1);

str_vector.empty();

This will only destroy objects of type string*. It will not destroy the
string objects pointed to by the pointers. Thus, if you do not manually
destroy them elsewhere, you have a leak.


Best

Kai-Uwe Bux

 

[Greg]

If I have a vector of string, is a call to 'empty()' sufficient to free
the all memory (i.e. no memory leaks)?

vector <string> str_vector;
str_vector.push_back("hello");
str_vector.push_back("world");

str_vector.empty();

And what if i have a vector of string pointer.
vecto <string*> str_vector;
string* str1= new string();
string* str2= new string();

str_vector.push_back(str1);
str_vector.push_back(str1);

str_vector.empty();

std::vector.empty() returns a bool result indicating whether the vector
is in fact empty. It has no effect on the vector or its contents. Call
clear() to erase a std::vector's contents.

Greg

 

[red floyd]

This empties the vector and destroys all string objects therein. Upon their
destruction, each of these string objects takes care of its own memory.
There are no leaks.

Sorry, Kai, but as Greg pointed out, it does nothing of the sort. It
checks the vector and returns a bool indicating whether it has any
contents. In this case, it should return false.

std::vector<>::clear(), on the other hand, would do what you describe.

 

[Kai-Uwe Bux]

Sorry, Kai, but as Greg pointed out, it does nothing of the sort. It
checks the vector and returns a bool indicating whether it has any
contents. In this case, it should return false.

std::vector<>::clear(), on the other hand, would do what you describe.

Thanks for catching that.


Best

Kai-Uwe Bux

 

[Howard Hinnant]

Sorry, Kai, but as Greg pointed out, it does nothing of the sort. It
checks the vector and returns a bool indicating whether it has any
contents. In this case, it should return false.

std::vector<>::clear(), on the other hand, would do what you describe.

str_vector.capcity() remains non-zero. Each string has returned its
memory, but the vector itself hasn't returned its memory to hold the
strings. If you care about that too you can subsequently:

vector<string>().swap(str_vector);

Indeed, if you're working with a string implemented with sso, and if all
of your strings were short, the call to clear() may not have freed any
memory at all.

-Howard