C++ char array scope

Question

char* pArray = nullptr;
{
    char buffer[64];
    sprintf_s(buffer,"Time: 123456");
    pArray = buffer;

}
cout<<pArray<<endl;

"Time: 123456" is displayed even though the buffer has been deallocated back to the stack. What is going on here? Is this safe? Not safe?

There are maybe another 20 or 30 posts here on SO asking the same question... — Mahmoud Al-Qudsi
– Mahmoud Al-Qudsi, Commented Apr 15, 2012 at 18:52

Luchian Grigore · Accepted Answer · 2012-04-15 18:43:09Z

2

It's undefined behavior. The memory probably isn't cleared.

It's pure luck your print statement works. When an object goes out of scope or is deleted, the memory is marked as released and not actually erased. The program can reclaim it and overwrite it.

answered Apr 15, 2012 at 18:43

Luchian Grigore

260k68 gold badges465 silver badges634 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

gulyan · Accepted Answer · 2012-04-15 18:46:21Z

0

You are not using the memory anymore, but the data is still there.

You should not do stuff like that unless you know what you're doing.

You can use a hack like that to pass some parameters to a function but it's very unsafe.

answered Apr 15, 2012 at 18:46

gulyan

6625 silver badges15 bronze badges

Collectives™ on Stack Overflow

C++ char array scope

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related