[dnb114@psu.edu: MarkInstall and AutoInst]

[Daniel Burrows <dnb114@psu.edu>]

  An update on this bug: I just sent this mail to debian-deity.  It
looks like this is either a bug or a deficiency in libapt; I am
currently awaiting feedback on which one it is.

  Daniel

----- Forwarded message from Daniel Burrows <dnb114@psu.edu> -----

From: Daniel Burrows <dnb114@psu.edu>
Subject: MarkInstall and AutoInst
To: debian-deity@lists.debian.org
Date: Thu, 4 Mar 2004 13:13:09 -0500

  This is something that came up in an aptitude bug report recently.
The behavior of MarkInstall in one corner case seems odd to me, and I
thought I should bring it up here.

  Say you have packages A, B, C, dependencies A->B and B->C.  All three
are installed, but have been marked for removal (MarkDelete).

  Now, call MarkInstall on A with AutoInst=true.  I would expect that B
and C would automatically be kept to satisfy the dependencies, but this
does not occur: A is installed, and B *is* kept, but C is left in the
Delete state, resulting in B being InstBroken.

  Calling MarkInstall on B (again with AutoInst=true) installs its
immediate dependencies (C in this case).  For longer dependency chains,
the pattern continues: the dependencies of C, for instance, remain in
the Delete state until C is marked for installation.

  It looks to me like the culprit is lines 612-614 of depcache.cc: after
calling MarkKeep, the routine immediately returns rather than
recursively checking the dependencies of the package.  There are a
number of plausible ways to approach this, assuming my diagnosis is
correct and that the current behavior is not intentional; I have
attached an entirely untested patch that demonstrates one approach.

  Daniel

-- 
/-------------------- Daniel Burrows <dburrows@debian.org> -------------------\
|        "Witches and pickles went together like...she hesitated at           |
|         the stomach-curdling addition of peaches and cream, and             |
|         mentally substituted 'things that went together very well'"         |
|          -- Terry Pratchett                                                 |
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--- apt-pkg/depcache.cc.old	2004-03-04 13:08:36.000000000 -0500
+++ apt-pkg/depcache.cc	2004-03-04 13:09:43.000000000 -0500
@@ -608,35 +608,37 @@
    P.iFlags &= ~AutoKept;
    if (P.InstBroken() == false && (P.Mode == ModeInstall ||
 	P.CandidateVer == (Version *)Pkg.CurrentVer()))
-   {
-      if (P.CandidateVer == (Version *)Pkg.CurrentVer() && P.InstallVer == 0)
+     {
+       if (P.CandidateVer == (Version *)Pkg.CurrentVer() && P.InstallVer == 0)
 	 MarkKeep(Pkg);
-      return;
-   }
-
-   // See if there is even any possible instalation candidate
-   if (P.CandidateVer == 0)
-      return;
-   
-   // We dont even try to install virtual packages..
-   if (Pkg->VersionList == 0)
-      return;
-   
-   /* Target the candidate version and remove the autoflag. We reset the
-      autoflag below if this was called recursively. Otherwise the user
-      should have the ability to de-auto a package by changing its state */
-   RemoveSizes(Pkg);
-   RemoveStates(Pkg);
-   
-   P.Mode = ModeInstall;
-   P.InstallVer = P.CandidateVer;
-   P.Flags &= ~Flag::Auto;
-   if (P.CandidateVer == (Version *)Pkg.CurrentVer())
-      P.Mode = ModeKeep;
+       // return;
+     }
+   else
+     {
+       // See if there is even any possible instalation candidate
+       if (P.CandidateVer == 0)
+	 return;
+   
+       // We dont even try to install virtual packages..
+       if (Pkg->VersionList == 0)
+	 return;
+   
+       /* Target the candidate version and remove the autoflag. We reset the
+	  autoflag below if this was called recursively. Otherwise the user
+	  should have the ability to de-auto a package by changing its state */
+       RemoveSizes(Pkg);
+       RemoveStates(Pkg);
        
-   AddStates(Pkg);
-   Update(Pkg);
-   AddSizes(Pkg);
+       P.Mode = ModeInstall;
+       P.InstallVer = P.CandidateVer;
+       P.Flags &= ~Flag::Auto;
+       if (P.CandidateVer == (Version *)Pkg.CurrentVer())
+	 P.Mode = ModeKeep;
+       
+       AddStates(Pkg);
+       Update(Pkg);
+       AddSizes(Pkg);
+     }
    
    if (AutoInst == false)
       return;


----- End forwarded message -----

-- 
/-------------------- Daniel Burrows <dburrows@debian.org> -------------------\
|                      Put no trust in cryptic comments.                      |
\------------- Got APT? -- Debian GNU/Linux http://www.debian.org ------------/