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| author | Simon Marlow <simonmar@microsoft.com> | 2008-09-27 14:18:34 +0000 |
|---|---|---|
| committer | Simon Marlow <simonmar@microsoft.com> | 2008-09-27 14:18:34 +0000 |
| commit | cd85694dcc3fd0cccbba84421185b41ae7fd762a (patch) | |
| tree | 9c3295d981612ae8e2f5b5d5c4570a8bce2837a7 | |
| parent | bb074cb7f881ab865e9fba04ab7244a3951d3494 (diff) | |
| download | haskell-cd85694dcc3fd0cccbba84421185b41ae7fd762a.tar.gz | |
tweaks to this section of the docs
| -rw-r--r-- | docs/users_guide/separate_compilation.xml | 44 |
1 files changed, 22 insertions, 22 deletions
diff --git a/docs/users_guide/separate_compilation.xml b/docs/users_guide/separate_compilation.xml index 8f14358379..727a133655 100644 --- a/docs/users_guide/separate_compilation.xml +++ b/docs/users_guide/separate_compilation.xml @@ -299,7 +299,7 @@ <replaceable>dir</replaceable>. For example:</para> <screen> -$ 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` </screen> <para>The object files, <filename>Foo.o</filename>, @@ -579,9 +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 <command>make</command>. When an interface does change, it is often enlightening to be informed. The - <option>-ddump-hi-diffs</option> option will make GHC run - <command>diff</command> on the old and new - <filename>.hi</filename> files.</para> + <option>-ddump-hi-diffs</option> option will make GHC + report the differences between the old and + new <filename>.hi</filename> files.</para> </listitem> </varlistentry> @@ -661,24 +661,24 @@ $ ghc -c parse/Foo.hs parse/Bar.hs gurgle/Bumble.hs -odir `arch` <literal>B</literal>, say) may conceivably not change <filename>B.hi</filename> one jot. So now…</para> - <para>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 <filename>.o</filename> - 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!</para> - - <para>Patrick Sansom had a workshop paper about how all this is - done (though the details have changed quite a bit). <ulink - url="mailto:sansom@dcs.gla.ac.uk">Ask him</ulink> if you want a - copy.</para> + <para>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 <filename>.o</filename> 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!</para> + + <para>You can read + about <ulink url="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoidance">how + all this works</ulink> in the GHC commentary.</para> </sect2> |