[Bug c++/19351] operator new[] can return heap blocks which are too small

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2005-01-09 22:48 -------
I also wonder what the semantics are that you are expecting? I mean,  
you try to allocate an array that is so large that you can't address  
the individual bytes using a size_t, in other words one that is larger   
than the address space the OS provides to your program. That clearly  
doesn't make any sense.  
  
That being said, I understand that the behavior of this is security  
relevant and that any attempt to allocate more memory than is available  
will necessarily have to fail. Thus, our present implementation isn't  
standards conforming, since it returns a reasonable pointer even in  
the case that the allocation should have failed. I would therefore agree  
that this is a problem, and given that memory allocation is an expensive  
operation, one overflow check isn't really time critical.  
  
Unfortunately, the situation is not restricted to libstdc++'s implementation  
of operator new[], since that operator only gets the total size of  
the memory to be allocation, not the size per element and the number of  
elements. Therefore, by the time we get into the implementation of this  
operator, it is already too late. In other words, the overflow check has  
to happen in compiler-generated code, not in the libstdc++ implementation.  
  
I would support the introduction of such code, if necessary guarded by  
some flag, or unconditionally, as a matter of quality of implemetation.  
  
W.  

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-01-09 22:48:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351