On Wed, 2018-12-26 at 10:15 +0000, Kumara, Asanka wrote:
> Hi,
> Is there a way to detect ALL dangling pointers (at exit) in valgrind ?
>
> e.g.
>
> char* globalVar;
>
> void main()
> {
> char* z1 = new char[10];
> char* z2 = z1;
> globalVar = z2;
>
> delete[] z1;
>
> }
>
> At exit of the program say that “globalVar” holds a pointer to a freed memory.
No, this feature does not exist.
I do not think that it would be very difficult to implement: it would basically
be the same algorithm as the leak search, but instead of searching for pointers
pointing at allocated blocks, the search should find the pointers pointing
at recently freed blocks.
That being said, it means that you will only find the dangling pointers
pointing in the recently freed blocks list, as dimensioned with
--freelist-vol=<number> volume of freed blocks queue [20000000]
So, you would only have a guarantee to detect ALL dangling pointers if
the free list volume is big enough to hold all blocks that were freed during
the run of the program.
And of course, as valgrind implements an optimistic leak search, you would
get an 'optimistic dangling pointer search' : on a 64 bits platform, any
aligned 8 bytes
(e.g. integer, char array, ...) might be considered by 'luck' as pointing to
a recently freed block, giving a false positive dangling pointer.
Philippe
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