[PATCH] fix singular iterator dereference in libstdc++ testcase 23_containers/list_modifiers.cc

[Doug Gregor <dgregor at apple dot com>]

In the testcase 23_containers/list_modifiers.cc, the function test01() 
contains this block of code:

  list0101.pop_back();          // list should be [2 1]
  VERIFY(list0101.size() == 2);
  VERIFY(T::dtorCount() == 1);
  VERIFY(i->id() == 1);
  VERIFY(j->id() == 1); // INVALID
  VERIFY(k->id() == 1);

Prior to the pop_back() call, the list is [2 1 3]  and the iterators i 
and k, along with reverse_iterator j, point to the 1. However, the 
actual iterator that j stores (in j.current) points to the 3, which is 
invalidated by the pop_back() call, and therefore should not be 
dereferenced at the line marked INVALID. The same problem occurs again 
in the next block (j.current is still singular).

Note that the problem does not show up as a failure in normal test 
runs, presumably because the old node is still accessible in memory due 
to the pooling allocator.

Patch & changelog entry attached.

	Doug

Attachment: list_modifiers_invalid.ChangeLog
Description: Binary data

Attachment: list_modifiers_invalid.patch
Description: Binary data