scope of variable outside for loop

Question

I'm trying to use a program written a few years ago and compiled in a previous version of MS VC++ (I am using VC++ 2008). There are a lot (hundreds) of instances similar to the following:

int main () {
  int number = 0;
  int number2 = 0;

  for (int i = 0; i<10; i++) {
   //something using i
  }

  for (i=0; i<10; i++) {
   //something using i
  }

  return 0;
}

I'm not sure which version it was originally compiled in, but it worked. My question is: how did it work? My understanding is that the i variable should only be defined for use in the first loop. When I try to compile it now I get the error "'i': undeclared identifier" for the line starting the second loop, which makes sense. Was this just overlooked in previous versions of VC++? Thanks!

Community · Accepted Answer · 2017-05-23 12:04:10Z

5

An earlier version of MSVC had this "misfeature" in that it leaked those variables into the enclosing scope.

In other words, it treated:

for (int i = 0; i<10; i++) {
    // something using i
}

the same as:

int i;
for (i = 0; i<10; i++) {
    // something using i
}

See the answers to this question I asked about a strange macro definition, for more detail.

edited May 23, 2017 at 12:04

CommunityBot

11 silver badge

answered Oct 14, 2010 at 16:53

paxdiablo

888k243 gold badges1.6k silver badges2k bronze badges

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

3 Comments

Jade Over a year ago

Ok thanks. That makes sense. Not really looking forward to changing all those errors...

paxdiablo Over a year ago

Maybe a global search and replace for for (i = with for (int i = ? Though that may give you errors going the other way.

Jade Over a year ago

Your previously asked question was very insightful, thanks for the link! Maybe you're right, doing that search and replace will probably be less work, even if I have to go back and fix some other resultant errors.

Collectives™ on Stack Overflow

scope of variable outside for loop

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related