Hi Eric,
definitely not bit-rotted - the #if DEBUG code is what you get when you
compile with -debug.
Short roadmap:
In general, GHC is built in many "ways", the -debug way is one.
Some ways (like -threaded, -eventlog, -debug) are RTS-only, others (like
-prof) lead to different library code.
Ways are defined in compiler/main/DynFlags.hs as a Haskell data structure.
In _dynamic_flags_, the actual flag strings for the ghc invocation are
defined (like -prof, -threaded), they will activate the respective _Way_.
_wayTag_, in turn, defines short names used as a suffix for *.o and *.a
files, for instance *.p_o for profiling, *.l_o for eventlog.
A number of other functions in there customise behaviour depending on
the ways. Note _wayOptc_ which sets some options for the C compiler,
like -DTRACING for the -eventlog way. However, it does not define DEBUG
for the debug way!
In mk/ways.mk you will find all the short names, and some more options
are defined (WAY_*_HC_OPTS). These definitions are for the driver
script, and pass on the right (long-name) options to the Haskell
compiler to activate what is inside DynFlags (like -prof for WAY_p_HC_OPTS).
Here we find
WAY_debug_HC_OPTS= -static -optc-DDEBUG -ticky -DTICKY_TICKY
which is what you were looking for
To build a GHC with debug-way RTS, you need to add GhcRtsWays += debug
to your build.mk (also see mk/config.mk{.in}, which gathers the default
ways to build depending on platform and build configuration).
I guess this might produce quite a number of new warnings and errors if
you do it on a new platform...
Once you have built this, you can compile with -debug and pass RTS
options to get debug traces and activate sanity checks, like so:
ghc -debug -myprogram.hs -o myprogramDebug
./myprogramDebug +RTS -Ds -DS
(-DS = sanity checks on, -Ds = scheduler tracing)
The usage message (see /rts/RtsFlags.c) tells you more options you can use.
Happy debugging!
/ Jost
On 05/14/2015 10:00 PM, ghc-devs-requ...@haskell.org wrote:
Date: Thu, 14 May 2015 18:36:04 +1000
From: Erik de Castro Lopo <mle...@mega-nerd.com>
To: ghc-devs@haskell.org
Subject: Debugging the RTS
Message-ID: <20150514183604.2476baaaacd6a85ef1430...@mega-nerd.com>
Content-Type: text/plain; charset=US-ASCII
Hi all,
I'm trying to debug a AArch64/Linux specific RTS issue and digging
around in the rts C code, I see a large amount of code wrapped in
"#if DEBUG" type statements, but no way to enable in either
mk/build.mk or it seems in any of the other build related settings
files in the mk/ directory.
The only way I have found to enable this debug code that actually
works is to enable this DEBUG code is to edit mk/ghc.mk as follows:
-STANDARD_OPTS += -DCOMPILING_RTS
+STANDARD_OPTS += -DCOMPILING_RTS -DDEBUG
However, once I do that I get a bunch of C synatx errors.
I am doing this wrong or has the DEBUG code bit rotted?
Cheers,
Erik
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