[commit: testsuite] master: Explain skipping compiler-perf tests when debugging is on (14958ae)

[Simon Marlow]

On 29/11/2013 10:28, Joachim Breitner wrote:
> Hi,
>
> Am Freitag, den 29.11.2013, 10:08 +0000 schrieb Simon Marlow:
>> Actually this isn't quite right.  compiler_debugged() is true when
>> GhcDebugged=YES in the build system, and GhcDebugged controls whether
>> GHC is compiled with -debug or not.
>>
>> That is, compiler_debugged() tells us whether the compiler was compiled
>> with -debug, not -DDEBUG.  The -debug flag links in the debug RTS and
>> doesn't change allocation or heap residency, whereas -DDEBUG enables
>> assertions in the compiler and *does* change allocation and heap residency.
>>
>> It looks like we need another predicate to tell us whether GHC was
>> compiled with -DDEBUG or not.
>>
>> Would you mind backing out these changes in the meantime?
>
> are you sure? compiler_debugged() is certainly true when I build ghc
> with
>          GhcStage2HcOpts    = -O0 -DDEBUG
> which yields
>          ./inplace/bin/ghc-stage2 --info|grep 'Debug on'
>           ,("Debug on","True")
> but
>          ./inplace/bin/ghc-stage2 +RTS --info|grep -i debug
> is empty.
>
> The test runner sets the value testsuite/mk/ghc-config.hs:
>    info <- readProcess ghc ["--info"] ""
>    let fields = read info :: [(String,String)]
>    getGhcFieldOrFail fields "GhcDebugged" "Debug on"
> which writes to testsuite/mk/ghcconfig_*
> which is then read by testsuite/mk/boilerplate.mk
> which is included everywhere
> including mk/test.mk which sets "-e ghc_debugged=$(GhcDebugged)"

Oh, we use the same variable name GhcDebugged to mean two different 
things: in the GHC build system it means that GHC was compiled with 
-debug, but in the testsuite build system it means that GHC was compiled 
with -DDEBUG.  How confusing!

Anyway you're right - there doesn't seem to be a bug, but we should 
rename things to avoid confusion.  I'll do that.

> So it seems that it is simply the wiki documentation that is wrong here.

I didn't check the wiki, just got confused by the source.  Please go 
ahead and fix the wiki if there's something wrong there.

Cheers,
Simon