Re: [Valgrind-users] What does this mean: malloc with N1 bytes inside a block of size N2 alloc'd

[David C. <dcc...@ac...>]

On 12/2/2011 10:51 PM, Yuri wrote:
> On 12/02/2011 22:29, Brad Hards wrote:
>> So if you provide detailed information such as the exact trace, we might be
>> able to do something other than guess.
> I pretty much explained the stack. Well, here it is verbatim:

What is the actual error you are getting?  You have never told us what 
the error is.  This shows only the address that memcheck thinks is being 
accessed improperly.

Is this the first error, or are there other messages from memcheck 
before this one?  If the memory allocator is so confused that it is 
allocating memory that has not yet been freed, memory is pretty well 
corrupted.  In this case, the first messages are the only ones that are 
really reliable; other messages may result from the memory corruption 
itself.

If you write far enough outside the bounds of an allocated memory block, 
you might start to write into another allocated memory block.  memcheck 
isn't smart enough to know which memory block should be accessed, so it 
guesses.  It may have allowed an improper memory write without flagging it.

We need to see the error message itself as well as the full call chain 
(stack) before we can even start to help.  The stack chain you printed 
is incomplete; it should go all the way up to main().  You've only 
showed us the stack up to the allocator routine in the standard C 
llibrary routine.

-- 
     David Chapman         dcc...@ac...
     Chapman Consulting -- San Jose, CA