mut_list_size calculation is off

Program:

main = print (foldr (+) 0 [ 0 .. 10000 ] :: Int)

Compile:

$ ghc-stage2 Main.hs -debug -rtsopts -O0

Run:

$ ./Main +RTS -Dg

It prints something like

mut_list_size: 16 (0 vars, 0 arrays, 0 MVARs, 0 TVARs, 0 TVAR_WATCH_QUEUEs, 0 TREC_CHUNKs, 0 TREC_HEADERs, 0 ATOMIC_INVARIANTs, 0 INVARIANT_CHECK_QUEUEs, 0 others)

So there are two objects in the mut list, but scavenge_mutable_list wasn't able to find anything. This is curious, and it seems like a bug.

Pretty much any program has this bug, mut_list_size and sum of objects found in the mut list never match.

Trac metadata

Trac field	Value
Version	8.5
Type	Bug
TypeOfFailure	OtherFailure
Priority	lowest
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	bgamari, simonmar
Operating system
Architecture