[Bug 1972043] Re: Please add -ftrivial-auto-var-init=zero to default build flags

[Andres Freund]

FWIW, I recently measured the overhead of -ftrivial-auto-var-init=zero
for postgres, and the overhead for *some* workloads could not fairly be
described with "nearly no overhead". For read-only OLTP the overhead was
in the 1-3% range, but for OLAP style queries it was higher, between
0-20% for  the different queries in TPC-H.

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Title:
  Please add -ftrivial-auto-var-init=zero to default build flags

Status in dpkg package in Ubuntu:
  Confirmed
Status in gcc-12 package in Ubuntu:
  Confirmed
Status in dpkg source package in Kinetic:
  Confirmed
Status in gcc-12 source package in Kinetic:
  Confirmed

Bug description:
  Please add "-ftrivial-auto-var-init=zero" for GCC 12 (which is the
  first release of GCC to provide this flag).

  It goes well with the other important security flaw mitigation flags already enabled in Ubuntu for GCC:
  https://wiki.ubuntu.com/ToolChain/CompilerFlags

  While many variables are initialized (due to -Wuninitialized), there
  is a blind spot for variables passed by reference, padding, and cases
  where -Wuninitialized just fails to track it. Universally wiping the
  variables eliminates nearly the entire class of uninitialized stack
  variable use (https://cwe.mitre.org/data/definitions/457.html) with
  nearly no overhead (e.g. any duplicate assignments will already be
  squashed during dead store elimination, etc).

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