Avoid memcpy() with same source and destination during relmapper init.
authorTom Lane <[email protected]>
Fri, 18 Dec 2020 20:46:44 +0000 (15:46 -0500)
committerTom Lane <[email protected]>
Fri, 18 Dec 2020 20:46:44 +0000 (15:46 -0500)
commit94aaa79afe656e6845d3c8af0befa8922edae0e8
tree0e11419a1e5e312d950c39276bce1d8036573412
parentda7edca4630c5bcf7c0f0f5819ab6fb020d3c845
Avoid memcpy() with same source and destination during relmapper init.

A narrow reading of the C standard says that memcpy(x,x,n) is undefined,
although it's hard to envision an implementation that would really
misbehave.  However, analysis tools such as valgrind might whine about
this; accordingly, let's band-aid relmapper.c to not do it.

See also 5b630501ed3f4e8a8aad7b48ea0, and other similar fixes.
Apparently, none of those folk tried valgrinding initdb?  This has been
like this for long enough that I'm surprised it hasn't been reported
before.

Back-patch, just in case anybody wants to use a back branch on a platform
that complains about this; we back-patched those earlier fixes too.

Discussion: https://postgr.es/m/161790.1608310142@sss.pgh.pa.us
src/backend/utils/cache/relmapper.c