id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5626	Miscompilation, exception omitted with -O	michal.palka	simonpj	"Following program is miscompiled when compiled with `-O`.
{{{
module Main where

wrap x = [x]!!0

f :: [Int] -> a
f a = foldr (\b -> \c -> c) (undefined ()) (a ++ a) 0

main = do
  print $ (f [] :: String)
  print $ wrap $ (f [] :: Int)
  print $ wrap $ (f [] :: (Int, Int, Int, Int))
}}}

The result of running it on my machine (Linux x86-64) is following:
{{{
""
1099511628032
zsh: segmentation fault  ./test7
}}}

Looking at the Core it seems that instead of the expected `undefined` a partially-applied function is returned. GHC 7.3.20111022 was used for testing."	bug	closed	high	7.4.1	Compiler	7.3	fixed	strictness strict exception miscompilation	michal.palka@…	Unknown/Multiple	Unknown/Multiple	Incorrect result at runtime		codeGen/should_run/5626