Heap profiling - hp2ps: samples out of sequence

make TEST=hpc_fork WAY=prof is failing, but it has nothing to do with hpc.

hp2ps: hpc_fork.hp, line 9, samples out of sequence
hp2ps error when processing heap profile for hpc_fork

hpc_fork.hs:

module main where

import system.posix.process
import control.concurrent

main = do
  pid1 <- forkprocess $ do threaddelay 100000
  pid2 <- forkprocess $ do threaddelay 100000
  print ()

To reproduce:

$ ghc-8.0.1 hpc_fork.hs -fforce-recomp -prof
$ ./hpc_fork +RTS -hc
$ hp2ps hpc_fork.hp

Example hpc_fork.hp:

JOB "hpc_fork +RTS -hc"
DATE "Thu Feb 25 22:37 2016"
SAMPLE_UNIT "seconds"
VALUE_UNIT "bytes"
BEGIN_SAMPLE 0.000000
END_SAMPLE 0.000000
BEGIN_SAMPLE 0.005672
END_SAMPLE 0.005672
BEGIN_SAMPLE 0.003167
END_SAMPLE 0.003167
BEGIN_SAMPLE 0.003311
END_SAMPLE 0.003311

This is a regression from 7.10.3.

Trac metadata

Trac field	Value
Version	8.0.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Profiling
Test case
Differential revisions
BlockedBy
Related	#664 (closed)
Blocking
CC
Operating system
Architecture