id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4283	Different behaviour with -O in concurrent program	simonpj	simonmar	"Mitar (mmitar@gmail.com) reports
I am attaching a program which locks (throws an exception <<loop>>) when compiled like:
{{{
ghc --make -threaded -main-is Test.main Test.hs -o test-no-opt -package mtl
}}}
and doesn't loop when compiled with
{{{
ghc --make -threaded -O2 -main-is Test.main Test.hs -o test-opt -package mtl
}}}
This should probably not happen.

I am using 6.12.3 on Linux x86_64.

SimonPJ reproduced this with the HEAD:
{{{
simonpj@cam-04-unx:~/tmp$ ./test-opt
42
42
42
42
-- Ctrl-C out
simonpj@cam-04-unx:~/tmp$ ./test-no-opt
42
test-no-opt: <<loop>>
/bin/bash: line 0: echo: write error: Broken pipe
/bin/bash: line 0: echo: write error: Broken pipe
/bin/bash: line 0: echo: write error: Broken pipe
-- Ctrl-C out
}}}
It's not 100% clear that it's a bug, but Simon M will look at it."	bug	closed	normal	7.4.1	Compiler	6.12.3	invalid		mmitar@…	Unknown/Multiple	Unknown/Multiple	None/Unknown