X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=docs%2Fusers_guide%2Fseparate_compilation.xml;h=32dc850e3cee88f5c69521c609419a6d1898c931;hp=bc3afcab6342807034f052804756e9287cb39ea5;hb=432b9c9322181a3644083e3c19b7e240d90659e7;hpb=e42d6cb48df657053029aff833de1151cf7349bf diff --git a/docs/users_guide/separate_compilation.xml b/docs/users_guide/separate_compilation.xml index bc3afca..32dc850 100644 --- a/docs/users_guide/separate_compilation.xml +++ b/docs/users_guide/separate_compilation.xml @@ -299,7 +299,7 @@ dir. For example: -$ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `arch` +$ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `uname -m` The object files, Foo.o, @@ -374,6 +374,20 @@ $ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `arch` + + + dir + + + + The option is shorthand for + the combination + of , , + and . + + + + suffix @@ -565,9 +579,9 @@ $ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `arch` the same as the old one; this is friendly to make. When an interface does change, it is often enlightening to be informed. The - option will make GHC run - diff on the old and new - .hi files. + option will make GHC + report the differences between the old and + new .hi files. @@ -647,24 +661,24 @@ $ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `arch` B, say) may conceivably not change B.hi one jot. So now… - GHC keeps a version number on each interface file, and on - each type 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 the recompilation checking is on, 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! - - Patrick Sansom had a workshop paper about how all this is - done (though the details have changed quite a bit). Ask him if you want a - copy. + GHC calculates a fingerprint (in fact an MD5 hash) of each + interface file, and of each declaration within the interface + file. It also keeps in every interface file a list of the + fingerprints 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 the recompilation + checking is on, GHC will be clever. It compares the fingerprints + on the things it needs this time with the fingerprints + 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 early in the process saying + “Compilation IS NOT required”. What a beautiful + sight! + + You can read + about how + all this works in the GHC commentary. @@ -1011,15 +1025,7 @@ M.o : X.hi-boot option below). The dependency generation phase of GHC can take some - additional options, which you may find useful. For historical - reasons, each option passed to the dependency generator from - the GHC command line must be preceded by - -optdep. For example, to pass -f - .depend to the dependency generator, you say - - -ghc -M -optdep-f -optdep.depend ... - + additional options, which you may find useful. The options which affect dependency generation are: @@ -1028,15 +1034,7 @@ ghc -M -optdep-f -optdep.depend ... Display a list of the cycles in the module graph. This is - useful when trying to eliminate such cycles. You do not need the -optdep prefix - for this flag. - - - - - - - Turn off warnings about interface file shadowing. + useful when trying to eliminate such cycles. @@ -1052,14 +1050,14 @@ ghc -M -optdep-f -optdep.depend ... - file + file Use file as the makefile, rather than makefile or Makefile. If file doesn't exist, mkdependHS creates it. We often use - to put the dependencies in + to put the dependencies in .depend and then include the file .depend into @@ -1067,21 +1065,8 @@ ghc -M -optdep-f -optdep.depend ... - - + Make extra dependencies that declare that files with suffix @@ -1090,13 +1075,14 @@ ghc -M -optdep-f -optdep.depend ... .<suf>_hi, or (for {-# SOURCE #-} imports) on .hi-boot. Multiple - flags are permitted. For example, - will make dependencies - for .hc on + flags are permitted. For example, + + will make dependencies + for .hs on .hi, - .a_hc on + .a_hs on .a_hi, and - .b_hc on + .b_hs on .b_hi. (Useful in conjunction with NoFib "ways".) @@ -1112,35 +1098,6 @@ ghc -M -optdep-f -optdep.depend ... - - - same as - - - - - - Regard modules imported from packages as unstable, @@ -1247,7 +1204,13 @@ These considerations lead to the following definition of an orphan module: -GHC will warn you if you are creating an orphan module, if you add `-fwarn-orphan-modules`. +If you use the flag , GHC will warn you +if you are creating an orphan module. +Like any warning, you can switch the warning off with , +and +will make the compilation fail if the warning is issued. + + You can identify an orphan module by looking in its interface file, M.hi, using the mode. If there is a [orphan module] on the