prevent MarkInstall of unsynced Multi-Arch:same siblings

Multi-Arch: same packages can be co-installed, but need to have the same
version for all installed packages (aka "siblings"). Otherwise the
unsynced versions will fight against each other and the auto-install as
wel as the problem resolver will later have to decide between holding the
packages or to remove one of the siblings (usually a foreign) taking a
bunch of packages (like the entire foreign setup) with them.

The idea here is now to be more pro-active: MarkInstall will fail for
a package if the siblings aren't synced, so we don't allow a situation
in which a resolver has to decide if to hold or to remove-upgrade under
the assumption that the remove-upgrade decision is always wrong and
doesn't deserve to be explored (expect valid out-of-syncs of course).

Thats a pretty bold move to take for a library which is used by
different solvers so this check is done in IsInstallOk and can be
overridden if front-ends want to.

1 files changed, 17 insertions, 13 deletions

diff --git a/apt-pkg/depcache.h b/apt-pkg/depcache.h
index 7358048ed..d9c95349b 100644
--- a/apt-pkg/depcache.h
+++ b/apt-pkg/depcache.h
@@ -442,16 +442,15 @@ class pkgDepCache : protected pkgCache::Namespace
    /** \return \b true if it's OK for MarkInstall to install
     *  the given package.
     *
-    *  See the default implementation for a simple example how this
-    *  method can be used.
-    *  Overriding implementations should use the hold-state-flag to cache
-    *  results from previous checks of this package - also it should
-    *  be used if the default resolver implementation is also used to
-    *  ensure that these packages are handled like "normal" dpkg holds.
+    *  The default implementation simply calls all IsInstallOk*
+    *  method mentioned below.
+    *
+    *  Overriding implementations should use the hold-state-flag to
+    *  cache results from previous checks of this package - if possible.
     *
     *  The parameters are the same as in the calling MarkInstall:
     *  \param Pkg       the package that MarkInstall wants to install.
-    *  \param AutoInst  needs a previous MarkInstall this package?
+    *  \param AutoInst  install this and all its dependencies
     *  \param Depth     recursive deep of this Marker call
     *  \param FromUser  was the install requested by the user?
     */
@@ -461,12 +460,8 @@ class pkgDepCache : protected pkgCache::Namespace
    /** \return \b true if it's OK for MarkDelete to remove
     *  the given package.
     *
-    *  See the default implementation for a simple example how this
-    *  method can be used.
-    *  Overriding implementations should use the hold-state-flag to cache
-    *  results from previous checks of this package - also it should
-    *  be used if the default resolver implementation is also used to
-    *  ensure that these packages are handled like "normal" dpkg holds.
+    *  The default implementation simply calls all IsDeleteOk*
+    *  method mentioned below, see also #IsInstallOk.
     *
     *  The parameters are the same as in the calling MarkDelete:
     *  \param Pkg       the package that MarkDelete wants to remove.
@@ -498,6 +493,15 @@ class pkgDepCache : protected pkgCache::Namespace
    pkgDepCache(pkgCache *Cache,Policy *Plcy = 0);
    virtual ~pkgDepCache();
 
+   protected:
+   // methods call by IsInstallOk
+   bool IsInstallOkMultiArchSameVersionSynced(PkgIterator const &Pkg,
+	 bool const AutoInst, unsigned long const Depth, bool const FromUser);
+
+   // methods call by IsDeleteOk
+   bool IsDeleteOkProtectInstallRequests(PkgIterator const &Pkg,
+	 bool const rPurge, unsigned long const Depth, bool const FromUser);
+
    private:
    bool IsModeChangeOk(ModeList const mode, PkgIterator const &Pkg,
 			unsigned long const Depth, bool const FromUser);