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RTS Configurations

The RTS can be built in several different ways, corresponding to global CPP defines. The flavour of the RTS is chosen by GHC when compiling a Haskell program, in response to certain command-line options: -prof, -threaded, etc.

The CPP symbols and their corresponding command-line flags are:

PROFILING

Enables profiling.
GHC option: -prof
RTS suffix: p

THREADED_RTS

Enables multithreading in the RTS, bound threads, and SMP execution.
GHC option: -threaded
RTS suffix: thr

DEBUG

Enables extra debugging code, assertions, traces, and the +RTS -D options.
GHC option: -debug
RTS suffix: debug

NO_REGS, USE_MINIINTERPRETER

Enables "unregisterised" compilation, i.e. via C with no mangler.
GHC option: -unreg
RTS suffix: u

So for example, libHSRts_thr_debug.a is the version of the runtime compiled with THREADED_RTS and DEBUG, and will be linked in if you use the -threaded and -debug options to GHC.

The ways that the RTS is built in are controlled by the GhcRTSWays Makefile variable.

Combinations

The following combinations are allowed:

• DEBUG with anything
• PROFILING only with NO_REGS, USE_MINIINTERPRETER

OLD ways

The following ways are bitrotted and currently don't work (GHC 6.6):

TICKY

Ticky-ticky profiling
GHC option: -ticky
RTS suffix: t

PAR, GRANSIM

Parallel Haskell
GHC option: -par
RTS suffix: mp, mg