Re: Reading uninitialized memory

[Torbjorn Granlund]

Andrew Vaught <address@hidden> writes:

  On 25 Jan 2002, Torbjorn Granlund wrote:
  
  > Andrew Vaught <address@hidden> writes:
  > 
  >      I'm guessing that zero is stored without limbs and that
  >   mpz_get_si() always reads whatever passes for a non-limb.  The value
  >   read from uninitialized memory is not used and doesn't affect the
  >   value of zero, but you could get rid of a read and the spurious
  >   error message from this and other bounds-checking programs.
  > 
  > Your analysis is correct.
  
     Here is a simple patch to avoid the problem:
  
I remain to be convinced that this problem should be patched in GMP.

It is an optimization to read memory speculatively, if we know it is
from a valid address.  It would be better to fix the checker program
to track undefined values and make sure they aren't actually used, or
else live with their inaccuracies.

-- 
Torbjörn