#530: configuration features ----------------------------+----------------------------------------------- Reporter: guest | Owner: Type: enhancement | Status: new Priority: normal | Milestone: Component: Cabal library | Version: 1.6.0.1 Severity: normal | Keywords: Difficulty: unknown | Ghcversion: Platform: | ----------------------------+----------------------------------------------- Currently Cabal has support for ''configuration flags''. This is a nice feature, but quite limited. It can only take a boolean value, and the flag must be manually set during ''Setup.hs configure''. Here I propose a more powerfull feature, that it is yet easy to use (and, hopefully, easy to implement). The idea is to add support for ''configuration features''. A configuration feature is similar to a ''configuration flag'', but with some important differences. == Example == {{{ data Feature = Bool | String }}} A feature block: {{{ Feature HAVE_URANDOM action: execute include-dirs: ... c-sources: features/urandom.c -- other possible properties, as listed in -- "Build information chapter", excluding `buildable` and -- `other-modules` -- The `action` property can have values `compile` (default) -- or `execute` }}} This means that I'm testing for a feature named ''HAVE_URANDOM'', and the testing requires to compile/build and then execute some code. == Rules == 1. If compilation fails, ''HAVE_URANDOM'' will have value ''Feature False''. If ''action'' property is ''compile'', then a successful compilation will result in ''HAVE_URANDOM'' having a value of ''Feature True''. 2. If ''action'' property is ''execute'' and the executable returns a value /= 1, then ''HAVE_URANDOM'' will have value ''Feature False''. 3. If ''action'' property is ''execute'' and executable write something on stdout, then ''HAVE_URANDOM'' will have value ''Feature string''. 4. Otherwise ''HAVE_URANDOM'' will have value ''Feature True''. This provides a small but useful subset of what can be obtained using ''autoconf'', with the advantages that it is much more declarative, integrated with Cabal and portable. -- Ticket URL: http://hackage.haskell.org/trac/hackage/ticket/530 Hackage http://haskell.org/cabal/ Hackage: Cabal and related projects