RFR: 8221149: os::malloc checks MallocCatchPtr outside of ifdef ASSERT block

[Thomas Stüfe]

Hi Stefan,

On Thu, Mar 28, 2019 at 8:47 AM Stefan Karlsson <stefan.karlsson at oracle.com>
wrote:

> Hi all,
>
> Please review this patch to move the MallocCatchPtr check into the ifdef
> ASSERT block, just like the other usages of it.
>
> http://cr.openjdk.java.net/~stefank/8221149/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8221149
>
>
Looks good. Note that you also could remove the test completely from
os::realloc for the oldptr!=NULL case (lines 764ff) since we allocated
using os::malloc(), which already does the test.


> A side note: Is the intention that MallocCatchPtr should find pointers
> to the memory address returned from ::malloc, or the memory address we
> hand out from os::malloc? Currently it's the latter and it's not obvious
> from the the code if this was the intention from the beginning.
>
>   704   // Wrap memory with guard
>   705   GuardedMemory guarded(ptr, size + nmt_header_size);
>   706   ptr = guarded.get_user_ptr();
>   707
>   708   if ((intptr_t)ptr == (intptr_t)MallocCatchPtr) {
>
>
I find the test as it is is more useful since usually one wants to follow
pointers one sees in the hotspot.

However, we may just test both pointers, yes? So, break if MallocCatchPtr
is either the outside or the inside pointer.

I am not really emotionally invested though :)

Cheers Thomas



> Thanks,
> StefanK
>