GHCi stdout bug when base package is not optimised

Reported by Igloo:

The problem from a couple of weeks ago, where ghci's hFlush command seems to be flushing a different stdout to the one that expressions evaluated by ghci write to, happens with a "quickest" build:

SRC_HC_OPTS     = -H64m -Onot -fasm
GhcStage1HcOpts = -O -fasm
GhcStage2HcOpts = -Onot -fasm
GhcLibHcOpts    = -Onot -fasm
GhcLibWays      =
SplitObjs       = NO

but not if libraries are optimised:

SRC_HC_OPTS     = -H64m -Onot -fasm
GhcStage1HcOpts = -O -fasm
GhcStage2HcOpts = -Onot -fasm
GhcLibHcOpts    = -O -fasm
GhcLibWays      =
SplitObjs       = NO

ghci004 is an example of a failing test (no output is printed if libraries are not optimised).

This seems completely illogical to me. I'd have expected such a bug would be caused by optimisation meaning stdout gets inlined somewhere or something. Very curious!

Trac metadata

Trac field	Value
Version	6.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown