#5929: Exciting arity warning when compiling with optimizations
-----------------------------------------------+----------------------------
Reporter: passalaqua | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1 | Keywords: Exciting
arity
Os: Unknown/Multiple | Architecture:
Unknown/Multiple
Failure: Incorrect warning at compile-time | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by michalt):
I've just looked at the code for arity analysis and it seems to work just
fine.
This doesn't seem to be a warning but a debugging message comming from a
```pprTrace``` whenever the fixed-point algorith for arity analysis goes
for
more than one iteration. I thought that ```pprTrace``` should be disabled
by
default, but it is defined as
{{{
pprTrace :: String -> SDoc -> a -> a
-- ^ If debug output is on, show some 'SDoc' on the screen
pprTrace str doc x
| opt_NoDebugOutput = x
| otherwise = pprDebugAndThen trace str doc x
}}}
and
{{{
opt_NoDebugOutput :: Bool
opt_NoDebugOutput = lookUp (fsLit "-dno-debug-output")
}}}
which, as far as I can see, means that ```pprTrace``` will print something
unless the user specifies ```-dno-debug-output```. IOW it will be enabled
by
default.
The attached patch enables the ```-dno-debug-output``` if GHC is compiled
without DEBUG. Also we could consider adding a flag to enable debug output
(i.e.
the opposite of ```-dno-debug-output```), such as ```-ddebug-output```.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5929#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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