`panic' with packages

Dear GHC team,

In my previous letter I wrote about a bug-like message in 
                                      cvs ghc-6-2-branch  of May 24

(the fragments of this letter are appended).

And in this situation GHC also responds badly if the user forgets
to include a package.

  > cd foo
  foo> ghci $pcpfoo $pcpdocon 

  performs correct.

And if the user forgets to include the package  docon,  then it 
happens
        foo> ghci $pcpfoo 

  Loading package foo ... linking ...
  /home/mechvel/t/u/lib/HSfoo.o: unknown symbol `__stginit_Prelude_'
  ghc-6.2.1: panic! (the `impossible' happened, GHC version 6.2.1):
        can't load package `foo'  
  Please report it as a compiler bug to glasgow-haskell-bugs@xxxxxxxxxxx,
  or http://sourceforge.net/projects/ghc/.

The package  foo  refers to something which is not loaded/included.
Probably, istead of writing about a  bug  it should report 
  "
  /home/mechvel/t/u/lib/HSfoo.o: unknown symbol `__stginit_Prelude_'
  Possible reason: some library or package is forgotten.
  "


-----------------
Serge Mechveliani
mechvel@xxxxxxxx




--------------------------------------------------------------
Having  docon-2.08-pre,  build it under  -O  as  install.txt  
specifies.

And I write in DoCon Manual how to organize a package for the user
example program which links DoCon library and package.

1. 
After installing DoCon, set the variables
  setenv doconc    ".../docon/source/docon.conf"
  setenv pcdocon   "-package-conf ${doconc}"
  setenv pcpdocon  "${pcdocon} -package docon"
2. 
Design  Makefile  for creating a user package  foo  
by compiling the modules
                           u/Root.hs
                           u/subdir/M.hs
and putting the interfaces and libraries to the directory  u/lib/
...
  ------------------------------------------------------------------
  module Root where                            -- in file  u/Root.hs

  import DExport   -- imports all entities of DoCon and many of GHC
  import M (m)     -- of the user project

  f = (m,m)

  intRoot :: Z -> Maybe Z
  intRoot    n =  let  (ps,exps) = unzip $ factor n
                  in
                  if  any (not . even) exps  then  Nothing
                  else
                    let  halfs = map (`quot` 2) exps
                    in
                    Just $ product $ zipWith power ps halfs

  ------------------------------------------------------------------
  module M where  m = True                    -- file  u/subdir/M.hs
  ------------------------------------------------------------------


-- The  Makefile  in the directory  u/  should be  ------------------

ghcBinDir = /home/mechvel/ghcCVS/inst/bin
...
doconc = /home/mechvel/docon/2.08/docon/source/docon.conf
s      = /home/mechvel/t/u
e      = $(s)/lib

ghc    = $(ghcBinDir)/ghc
ghcpkg = $(ghcBinDir)/ghc-pkg

pcdocon  = -package-conf $(doconc)
pcpdocon = $(pcdocon) -package docon

RANLIB   = ar -s
language = -fglasgow-exts ...
warnings = -fno-warn-overlapping-patterns ... 
idirs    = subdir
HCFlags  =  $(language) $(warnings)                            \
            -i$(idirs) -odir $(e) -hidir $(e)  -ddump-hi-diffs \
            +RTS $(space) -RTS  $(extraHCOpts) 
space       = -M55m
extraHCOpts =

pack = Package {name            = "\"foo\"",  \
                import_dirs     = ["\"$(e)\""],    \
                source_dirs     = [],              \
                library_dirs    = ["\"$(e)\""],    \
                hs_libraries    = ["\"HSfoo\""], \
                extra_libraries = [], \
                include_dirs    = [], \
                c_includes      = [], \
                package_deps    = [], \  
                extra_ghc_opts  = [$(extraPackOpts)], \
                extra_cc_opts   = [],                 \
                extra_ld_opts   = [] } 

extraPackOpts = $(pwarnings), $(planguage)

planguage = "\"-fglasgow-exts\"", ...
pwarnings = "\"-fno-warn-overlapping-patterns\"", ...

obj:
        if [ ! -d $(e) ]; then mkdir $(e); fi
        $(ghc) $(HCFlags) $(pcpdocon) --make Root  -package-name foo

foo:    obj
        rm -f  $(e)/libHSfoo.a $(e)/HSfoo.o
        ar -qc $(e)/libHSfoo.a $(wildcard $(e)/*.o)
        $(RANLIB)  $(e)/libHSfoo.a
        echo $(pack) | $(ghcpkg) -f $(s)/foo.conf -u -g
        $(ghcpkg) -f $(s)/foo.conf -l

clear:
        $(ghcpkg) -f $(s)/foo.conf -r foo
        rm -f  $(s)/foo.conf.old
        rm -rf $(e)
--------------------------------------------------------------------
...

Making  foo:      cd  .../u;    make foo

Similarly as for DoCon package, arrange the variables

  setenv fooc    "/home/mechvel/t/u/foo.conf"
  setenv pcfoo   "-package-conf ${fooc}"
  setenv pcpfoo  "${pcfoo} -package foo"

To run  intRoot  from the separate directory, say  foo,  command 

  cd  .../foo
  ghci $pcpfoo $pcpdocon
 
  Loading package base ... linking ... done.
  ...
  Loading package docon ... linking ... done.
  Loading package foo ... linking ... done.
  
  Prelude> Root.intRoot 16
  Just 4
...
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