-pgmc/a/l default options, other ideas

[Peter Tanski]

In compiler/main/DriverPipeline.hs, runPhase sets default options  
*even if the user has specified a different program with the -pgm  
option.  The example I ran into before was:

ghc -pgma yasm -opta "-ax86" -opta "-pgas" -opta "-fwin32" test.asm

In ghc, these options are stored together under 'dflags":

runPhase As stop dflags _basename _suff input_fn get_output_fn maybe_loc
   = do	let as_opts =  getOpts dflags opt_a

runPhase continues to add particular wired-in options as if the only  
program used is the default.  For example:
	SysTools.runAs dflags
		((map SysTools.Option as_opts)
			++ [ SysTools.Option "-c", ... ])


This design seems to work as far as people use GHC--I am probably the  
only complainer.  I understand the purpose of -pgm options is largely  
to use a non-standard *location* for a default program.  An  
alternative design, as if any alternative program might be used,  
might make users responsible for adding *all* necessary options for a  
user-defined -pgm .  For GHC-default includes and link-libraries, GHC  
might map the include-opt or link-opt for the -pgm over them with  
additional options, such as mapping str1 or str2 from -opt_dlink str1  
and -opt_dincl str2 over the defaults.  The order of the options  
might be preserved by maintaining the order of the options used in  
the command line.

Ghc may test for a simple equivalence to the default pgm program in  
runPhase (before passing it to SysTools.runAs or such).  If you  
wanted to test for a nonstandard program, as opposed to a nonstandard  
location for a default program ("/usr/local/bin/gcc" instead of  
default "/usr/bin/gcc"), the test would use a regex and only test the  
equivalence of the program name ("gcc").  If the test fails, the  
program isn't considered the default and the remaining default  
options will not be added in runPhase.


In order to gain more flexibility in choosing the default programs  
and default options, particularly Microsoft CL and Yasm, I am  
generating those programs and options into compiler/main/Config.hs.   
(As you know, Config.hs is generated by compiler/Makefile.)  By the  
way, I am adding a simple comment in Config.hs to alert users to the  
source of this generated file:

-- This file is generated by compiler/Makefile --

It might be possible, even preferable, to keep the program names and  
default options from Config.hs by storing them in a configuration  
file as "Simon" suggested storing them in package.conf in a comment- 
note in SysTools.hs.  For Win-GHC (as I am calling Windows-native  
GHC), it would probably be more "standard" to store them in the  
Registry; for other systems they might be stored in package.conf or a  
specialised initialisation file.


Cheers,
Pete