From 1b964925f0487b64c9e562d798f464ebdbf6f1c7 Mon Sep 17 00:00:00 2001 From: simonpj <unknown> Date: Tue, 24 Aug 1999 09:31:07 +0000 Subject: [PATCH] [project @ 1999-08-24 09:31:07 by simonpj] Document the -i effect on recompilation --- ghc/docs/users_guide/using.vsgml | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/ghc/docs/users_guide/using.vsgml b/ghc/docs/users_guide/using.vsgml index d6ccff53932c..b5b5a751dfaf 100644 --- a/ghc/docs/users_guide/using.vsgml +++ b/ghc/docs/users_guide/using.vsgml @@ -508,6 +508,8 @@ it looks. <tag>@-i<dirs>@</tag><nidx>-i<dirs> option</nidx> This flag prepends a colon-separated list of @dirs@ to the ``import directories'' list. +See also Section <ref id="recomp"> for the significance of using +relative and absolute pathnames in the @-i@ list. <tag>@-i@</tag> resets the ``import directories'' list back to nothing. @@ -614,18 +616,24 @@ signature within the interface file. It also keeps in every interface file a list of the version numbers of everything it used when it last compiled the file. If the source file's modification date is earlier than the @.o@ file's date (i.e. the source hasn't changed since the -file was last compiled), and you give GHC the @-recomp@<nidx>-recomp -option</nidx> flag, then GHC will be clever. It compares the version +file was last compiled), GHC will be clever. It compares the version numbers on the things it needs this time with the version numbers on the things it needed last time (gleaned from the interface file of the module being compiled); if they are all the same it stops compiling rather early in the process saying ``Compilation IS NOT required''. What a beautiful sight! -It's still an experimental feature (that's why @-recomp@ is off by -default), so tell us if you think it doesn't work. - -Patrick Sansom has a workshop paper about how all this is done. Ask +GHC <em>only</em> keeps detailed dependency information for ``user'' modules, +not for ``library'' modules. It distinguishes the two by a hack: a module +whose @.hi@ file has an absolute path name is considered a library module, +while a relative path name indicates a user module. So if you have a +multi-directory application, use <em>relative</em> path names in your +@-i@ path, to force GHC to record detailed dependency information. +Use absolute path names only for directories containing slowly-changing +library modules. + +Patrick Sansom had a workshop paper about how all this is done (though +the details have changed quite a bit). Ask him (email: <htmlurl name="sansom@@dcs.gla.ac.uk" url="mailto:sansom@@dcs.gla.ac.uk">) if you want a copy. -- GitLab