[GHC] #11798: Recompiling with -fhpc flag added does nothing

[GHC]

#11798: Recompiling with -fhpc flag added does nothing
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           Reporter:  drathier       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:  x86_64         |   Type of failure:  None/Unknown
  (amd64)                            |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 When you recompile without modifiying any source code, nothing happens, as
 expected. The file is already compiled, after all. If you then add the
 -fhpc flag, it still doesn't recompile, even though it now should generate
 .tix files. These files are now unexpectedly missing, until the source
 files are modified or the .o and .hi files are deleted, and the code is
 recompiled again with the -fhpc flag.

 reproduce:
 1. compile program
 2. compile program with -fhpc
 note: missing .tix file
 3. delete .hi and .o files
 4. compile program with -fhpc
 5. success; .tix file is generated

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11798>
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