Stack space overflow error in Haskell with a very small stack size

Question

The Haskell program

main=main>>main

fails with

2mem: Stack space overflow: current size 33624 bytes.
2mem: Use `+RTS -Ksize -RTS' to increase it.

33k seems quite small. The OS (via top) is reporting a total memory usage of 6G before failing. When I compile the program with ghc -rtsopts 2mem.hs and run it with ./2mem +RTS -K32M I sill get the same error.

I'm using ghc, version 8.0.1 on MacOS 10.11.6.

Why is the stack space so small and why doesn't -K32M increase it?

It hardly matters. Your program will blow the stack no matter how you run it. It's basically the same as main = main, but the later will produce a <<loop>> exception instead of a stack overflow. 33K is a pretty large stack for the way GHC uses it. — dfeuer
– dfeuer, Commented Dec 1, 2016 at 22:05
The reported stack size in the message is wrong. I thought this got fixed though. — Reid Barton
– Reid Barton, Commented Dec 1, 2016 at 22:09
@ReidBarton: a bug in ghc, maybe this one, although it is marked as "fixed"? Anyone familiar with the ghc bug tracking system? Is there a way to re-open a ticket? — nimi
– nimi, Commented Dec 1, 2016 at 22:36
Yes that's the one I was thinking of. I reopened the ticket. — Reid Barton
– Reid Barton, Commented Dec 1, 2016 at 22:47

Reid Barton · Accepted Answer · 2016-12-01 22:55:55Z

3

It's a bug in GHC; the reported stack size in the message is wrong. See https://ghc.haskell.org/trac/ghc/ticket/10445 and thanks for noticing that it's not actually fixed.

answered Dec 1, 2016 at 22:55

Reid Barton

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