stale .tix files can cause programs built with -fhpc to segfault

In some circumstances, programs built with -fhpc will segfault when old .tix files reference modules that no longer exist.

foo.hs

import Bar

main = print "Hello World"

Bar.hs

module Bar where

something = 1 :: Int

jwlato@compy:~/explorations$ ghc -O -fhpc foo.hs 
[1 of 2] Compiling Bar              ( Bar.hs, Bar.o )
[2 of 2] Compiling Main             ( foo.hs, foo.o )
Linking foo ...
jwlato@compy:~/explorations$ ./foo 
"Hello world"
jwlato@compy:~/explorations$ mv Bar.hs Bar.hs.orig
jwlato@compy:~/explorations$ sed -e 's/import/-- import/' -i.bak foo.hs 
jwlato@compy:~/explorations$ rm *.hi; rm *.o
jwlato@compy:~/explorations$ ghc -O -fhpc foo.hs 
[1 of 1] Compiling Main             ( foo.hs, foo.o )
Linking foo ...
jwlato@compy:~/explorations$ ./foo 
Segmentation fault

If "foo.hs" has a 'module Main where' declaration, instead of a segfault the program exits with a message that 'foo.tix' should be deleted.

Trac metadata

Trac field	Value
Version	7.4.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Code Coverage
Test case
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