Re: Consolidate 'unique array values' logic into a reusable function? - Mailing list pgsql-hackers

On Mon, Nov 04, 2019 at 12:02:21PM +1300, Thomas Munro wrote:
> Rebased.  I'm planning to commit this soon.

In each installcheck-parallel run under valgrind-3.14.0, I now see ~1200
reports like this:

==00:00:00:28.322 1527557== Source and destination overlap in memcpy(0x1000104, 0x1000104, 4)
==00:00:00:28.322 1527557==    at 0x4C2E74D: memcpy@@GLIBC_2.14 (vg_replace_strmem.c:1035)
==00:00:00:28.322 1527557==    by 0xA9A57B: qunique (qunique.h:34)
==00:00:00:28.322 1527557==    by 0xA9A843: InitCatalogCache (syscache.c:1056)
==00:00:00:28.322 1527557==    by 0xAB6B18: InitPostgres (postinit.c:682)
==00:00:00:28.322 1527557==    by 0x91F98E: PostgresMain (postgres.c:3909)
==00:00:00:28.322 1527557==    by 0x872DE9: BackendRun (postmaster.c:4498)
==00:00:00:28.322 1527557==    by 0x8725B3: BackendStartup (postmaster.c:4189)
==00:00:00:28.322 1527557==    by 0x86E7F4: ServerLoop (postmaster.c:1727)
==00:00:00:28.322 1527557==    by 0x86E0AA: PostmasterMain (postmaster.c:1400)
==00:00:00:28.322 1527557==    by 0x77CB56: main (main.c:210)
==00:00:00:28.322 1527557== 
{
   <insert_a_suppression_name_here>
   Memcheck:Overlap
   fun:memcpy@@GLIBC_2.14
   fun:qunique
   fun:InitCatalogCache
   fun:InitPostgres
   fun:PostgresMain
   fun:BackendRun
   fun:BackendStartup
   fun:ServerLoop
   fun:PostmasterMain
   fun:main
}

This is like the problem fixed in 9a9473f; the precedent from there would be
to test src!=dst before calling mempcy(), e.g. as attached.  I suppose the
alternative would be to add a suppression like the one 9a9473f removed.

I do wonder why the Valgrind buildfarm animals haven't noticed.