Hi,

I was working on making sure that allocations for [1] don't overflow
size_t for large hash tables, when created on 32bit systems.  I started
to write code like

if (sizeof(SH_CONTAINS) * (uint64) tb->size) !=
   sizeof(SH_CONTAINS) * (size_t) tb->size))
{
    elog(ERROR, "hash table too large for a 32 bit system");
}

that could code potentially, although somewhat unlikely, be trigger on a
32bit system.


That made me wonder if it's not actually a mistake for
MemoryContextAllocExtended() size parameter to be declared
Size/size_t. That prevents it from detecting such overflows, forcing
code like the above on callsites.

Comments?

- Andres

[1] 
http://archives.postgresql.org/message-id/20160727004333.r3e2k2y6fvk2ntup%40alap3.anarazel.de


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