Build system idea

[Malcolm Wallace]

Simon Marlow <marlowsd at gmail.com> wrote:

> This means we still get to use 'make', we still get to use the .cabal
> files  as metadata, but the build system is more private to GHC, more
> extensible,  and hopefully more understandable and modifiable.

This is essentially the same approach that nhc98 currently takes to
building libraries.  The Cabal file holds all the metadata, but the
build system is Makefile-driven.  There is a small separate tool
(CabalParse) that extracts metadata from the cabal file.  The Cabal
*library* could be used to implement that extraction tool, but currently
ours is hand-rolled.  (One of the benefits of open specifications of
file formats is that you can have multiple implementations for different
purposes.)

Here is an example of how it works:

CABALFILE  = $(shell ls *.cabal | head -n 1 )
READ       = $(CABALPARSE) $(CABALFILE) -quiet
MAP        = $(LOCAL)map

THISPKG    = $(shell $(READ) name | cut -c2- )
VERSION    = $(shell $(READ) version)
SEARCH     = $(shell $(READ) build-depends  | $(MAP) "echo -package" ) \
             $(shell $(READ) include-dirs   | $(MAP) "echo -i" | cut -c1,2,4-) \
             $(shell $(READ) hs-source-dir  | $(MAP) "echo -I" | cut -c1,2,4-) \
             $(shell $(READ) hs-source-dirs | $(MAP) "echo -I" | cut -c1,2,4-)
CINCLUDES  = $(shell $(READ) include-dirs   | $(MAP) "echo -I" | cut -c1,2,4-)
SRCS       = $(shell $(READ) -slash exposed-modules)
EXTRA_SRCS = $(shell $(READ) -slash other-modules)
SRCS_C     = $(shell $(READ) c-sources)
DIRS       = $(shell $(READ) -slash exposed-modules other-modules \
                     | $(MAP) dirname | sort | uniq )
EXTRA_C_FLAGS = $(shell $(READ) cc-options)
EXTRA_H_FLAGS = $(shell $(READ) nhc98-options)


Regards,
    Malcolm