3 files changed, 69 insertions, 23 deletions

diff --git a/libbuild2/cc/common.cxx b/libbuild2/cc/common.cxx
index d9afd21..934ea38 100644
--- a/libbuild2/cc/common.cxx
+++ b/libbuild2/cc/common.cxx
@@ -305,7 +305,9 @@ namespace build2
         //
         if (impl && !c_e_libs.defined () && !x_e_libs.defined ())
         {
+#if 0
           assert (top_li); // Must pick a member if implementation (see above).
+#endif
 
           for (const prerequisite_target& pt: l.prerequisite_targets[a])
           {
diff --git a/libbuild2/cc/link-rule.hxx b/libbuild2/cc/link-rule.hxx
index 23f7167..3d801d6 100644
--- a/libbuild2/cc/link-rule.hxx
+++ b/libbuild2/cc/link-rule.hxx
@@ -81,11 +81,10 @@ namespace build2
       class appended_libraries: public small_vector<appended_library, 128>
       {
       public:
-        // Find existing or append new entry. If appending new, use the second
-        // argument as the begin value.
+        // Find existing entry, if any.
         //
-        appended_library&
-        append (const file& l, size_t b)
+        appended_library*
+        find (const file& l)
         {
           auto i (find_if (begin (), end (),
                            [&l] (const appended_library& al)
@@ -93,19 +92,11 @@ namespace build2
                              return al.l2 == nullptr && al.l1 == &l;
                            }));
 
-          if (i != end ())
-            return *i;
-
-          push_back (appended_library {&l, nullptr, b, appended_library::npos});
-          return back ();
+          return i != end () ? &*i : nullptr;
         }
 
-        // Return NULL if no duplicate tracking can be performed for this
-        // library.
-        //
         appended_library*
-        append (const small_vector<reference_wrapper<const string>, 2>& ns,
-                size_t b)
+        find (const small_vector<reference_wrapper<const string>, 2>& ns)
         {
           size_t n (ns.size ());
 
@@ -125,8 +116,36 @@ namespace build2
                    : al.l1 == nullptr);
               }));
 
-          if (i != end ())
-            return &*i;
+          return i != end () ? &*i : nullptr;
+        }
+
+        // Find existing or append new entry. If appending new, use the second
+        // argument as the begin value.
+        //
+        appended_library&
+        append (const file& l, size_t b)
+        {
+          if (appended_library* r = find (l))
+            return *r;
+
+          push_back (appended_library {&l, nullptr, b, appended_library::npos});
+          return back ();
+        }
+
+        // Return NULL if no duplicate tracking can be performed for this
+        // library.
+        //
+        appended_library*
+        append (const small_vector<reference_wrapper<const string>, 2>& ns,
+                size_t b)
+        {
+          size_t n (ns.size ());
+
+          if (n > 2)
+            return nullptr;
+
+          if (appended_library* r = find (ns))
+            return r;
 
           push_back (appended_library {
               n == 2 ? &ns[1].get () : nullptr, &ns[0].get (),
diff --git a/libbuild2/cc/pkgconfig.cxx b/libbuild2/cc/pkgconfig.cxx
index 9177dbb..3fcfb9a 100644
--- a/libbuild2/cc/pkgconfig.cxx
+++ b/libbuild2/cc/pkgconfig.cxx
@@ -1642,9 +1642,10 @@ namespace build2
           struct data
           {
             ofdstream&           os;
-            appended_libraries&  ls;
+            appended_libraries*  pls; // Previous.
+            appended_libraries*  ls;  // Current.
             strings&             args;
-          } d {os, ls, args};
+          } d {os, nullptr, &ls, args};
 
           auto imp = [&priv] (const target&, bool la) {return priv && la;};
 
@@ -1656,17 +1657,31 @@ namespace build2
           {
             const file* l (lc != nullptr ? &(*lc)->as<file> () : nullptr);
 
+            // Suppress duplicates from the previous run (Libs/Libs.private
+            // split).
+            //
+            if (d.pls != nullptr)
+            {
+              // Doesn't feel like we can prune here: we may have seen this
+              // interface library but not its implementation dependencies.
+              //
+              if ((l != nullptr
+                   ? d.pls->find (*l)
+                   : d.pls->find (ns)) != nullptr)
+                return true;
+            }
+
             // Suppress duplicates (see append_libraries() for details).
             //
             // Note that we use the original name for duplicate tracking.
             //
             appended_library* al (l != nullptr
-                                  ? &d.ls.append (*l, d.args.size ())
-                                  : d.ls.append (ns, d.args.size ()));
+                                  ? &d.ls->append (*l, d.args.size ())
+                                  : d.ls->append (ns, d.args.size ()));
 
             if (al != nullptr && al->end != appended_library::npos)
             {
-              d.ls.hoist (d.args, *al);
+              d.ls->hoist (d.args, *al);
               return true;
             }
 
@@ -1697,9 +1712,12 @@ namespace build2
             //@@ TODO: how will the Libs/Libs.private work?
             //@@ TODO: remember to use escape()
 
+            if (d.pls != nullptr && d.pls->find (l) != nullptr)
+              return true;
+
             // See link_rule::append_libraries().
 
-            if (d.ls.append (l, d.args.size ()).end != appended_library::npos)
+            if (d.ls->append (l, d.args.size ()).end != appended_library::npos)
               return true;
 
             return true;
@@ -1723,9 +1741,16 @@ namespace build2
           {
             os << "Libs.private:";
 
-            ls.clear ();
             args.clear ();
             priv = true;
+
+            // Use previous appended_libraries to weed out entries that are
+            // already in Libs.
+            //
+            appended_libraries als;
+            d.pls = d.ls;
+            d.ls = &als;
+
             process_libraries (a, bs, li, sys_lib_dirs,
                                l, la, 0, // Link flags.
                                imp, lib, opt, false /* self */, &lib_cache);