push_back failing in VC6

Question

I know VC6 is 20th century technology, but for some special reasons that's the compiler I have to use.

I have the following code, which works just fine in Visual Studio Express 2008 (32 bits)

while( sqlite3_step( stmt ) == SQLITE_ROW ) {
  int tmp;
  tmp = sqlite3_column_int64( stmt, 0 );
  if(DEBUG) { cout  << "KeyID - " << tmp << endl ; };
  keyIDs.push_back(tmp);
  if(DEBUG) { cout  << "Size keyIDs - " << keyIDs.size() << endl ; };
}

In this particular test case, there's only one record, so the output, as you might expect, is

KeyID - 1
Size keyIDs - 1

However, if I compile the whole stuff (included sqlite3) with VC6 (32 bits), I have the following result:

KeyID - 1
Size keyIDs - 0

keyIDs is defined as

vector<sqlite3_int64> keyIDs;

but we even tried changing it to

vector<int> keyIDs;

I'm running out of ideas on what can be wrong, so I accept even wild guesses?

EDIT:

We solved this problem by using a local vector (keyIDs is a class member). Somehow, some piece of code elsewhere that I don't feel like tracking was (possibly) corrupting the vector, rendering it useless. Why this is happening only with VC6? That will remain a mystery.

EDIT2:

Although I haven't got to the root cause, I did find another problem (in a different proyect) with a large string (2800+ chars) passed to a function. The function itself received something like

function("something"+largestring+"anotherstring")

and this caused a memory exception elsewhere (coincidently, with a vector). It was solved by doing

largestring = "something";
largestring += stuff;
largestring += "anotherstring";

function (largestring);

In conclussion, it seems that something is wrong when VC6 creates a large object in the heap, and this may corrupt memory.

I hope this helps someone who, like me, is stuck with VC6 and is finding obscure errors.