[Bug c++/15054] New: Bad code due to overlapping stack temporaries

[uweigand at gcc dot gnu dot org]

The testcase appended below triggers the abort,
because two temporaries that are concurrently
used get assigned the same stack slot; thus the
constructor of the 'pointer' temporary built
inside the 'element' destructor will clobber
the 'canary' member of the current 'element'.

To reproduce, build the file with -O (both
-O0 and -O2 work correctly).



extern "C" void abort (void);

struct pointer
{
  void* ptr;

  pointer(void* x = 0) : ptr(x) {}
  pointer(const pointer& x) : ptr(x.ptr) {}
};

struct element
{
  int canary;

  element() : canary(123) { }
  ~element() { pointer(); if (canary != 123) abort (); }
};

inline pointer
insert(const element& x)
{
  return pointer(new element(x));
}

int
main (void)
{
  insert(element());
  return 0;
}

-- 
           Summary: Bad code due to overlapping stack temporaries
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: uweigand at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: s390-ibm-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15054