Allow holes in group_view array

4 files changed, 50 insertions, 13 deletions

diff --git a/libbuild2/algorithm.cxx b/libbuild2/algorithm.cxx
index e1f30e0..75540ff 100644
--- a/libbuild2/algorithm.cxx
+++ b/libbuild2/algorithm.cxx
@@ -2390,8 +2390,16 @@ namespace build2
     group_view gv (g.group_members (a));
     if (gv.count != 0)
     {
-      ep = gv.members[0]->as<file> ().path () + ".d";
+      for (size_t i (0); i != gv.count; ++i)
+      {
+        if (const target* m = gv.members[i])
+        {
+          ep = m->as<file> ().path () + ".d";
+          break;
+        }
+      }
 
+      assert (!ep.empty ());
       if (rmfile (ctx, ep, 3))
         er = target_state::changed;
     }
diff --git a/libbuild2/target.hxx b/libbuild2/target.hxx
index 55b8270..17a99d3 100644
--- a/libbuild2/target.hxx
+++ b/libbuild2/target.hxx
@@ -55,6 +55,14 @@ namespace build2
 
   // A view of target group members.
   //
+  // Note that the members array may have "holes" (NULL pointers) and count is
+  // the number of elements in this array (and not necessarily the number of
+  // group members).
+  //
+  // Note that members being NULL and count being 0 have different meaning:
+  // the former means group members are not known while the latter means it's
+  // an empty group.
+  //
   struct group_view
   {
     const target* const* members; // NULL means not yet known.
diff --git a/libbuild2/target.ixx b/libbuild2/target.ixx
index 94c54c0..f9db558 100644
--- a/libbuild2/target.ixx
+++ b/libbuild2/target.ixx
@@ -399,9 +399,14 @@ namespace build2
 
     if (k_ == nullptr && g_.count != 0) // Iterating over a normal group.
     {
-      if (g_.members == nullptr || // Special case, see leave_group().
-          ++j_ > g_.count)
+      if (g_.members == nullptr) // Special case, see leave_group().
         g_.count = 0;
+      else
+      {
+        for (++j_; j_ <= g_.count && g_.members[j_ - 1] == nullptr; ++j_) ;
+        if (j_ > g_.count)
+          g_.count = 0;
+      }
     }
 
     if (k_ == nullptr && g_.count == 0) // Iterating over the range.
@@ -443,8 +448,11 @@ namespace build2
         return false;
       }
 
-      if (g_.count != 0) // Group is not empty.
-        j_ = 0; // Account for the increment that will follow.
+      // Note: 0-based to account for the increment that will follow.
+      //
+      for (j_ = 0; j_ != g_.count && g_.members[j_] == nullptr; ++j_) ;
+      if (j_ == g_.count)
+        g_.count = 0;
     }
 
     return true;
@@ -474,10 +482,21 @@ namespace build2
   inline bool prerequisite_members_range<T>::iterator::
   group () const
   {
-    return
-      k_ != nullptr ? k_->adhoc_member != nullptr            : /* ad hoc   */
-      g_.count != 0 ? g_.members != nullptr && j_ < g_.count : /* explicit */
-      false;
+    // Ad hoc.
+    //
+    if (k_ != nullptr)
+      return k_->adhoc_member;
+
+    // Explicit.
+    //
+    if (g_.count != 0 && g_.members != nullptr)
+    {
+      size_t j (j_ + 1);
+      for (; j <= g_.count && g_.members[j - 1] == nullptr; ++j) ;
+      return j <= g_.count;
+    }
+
+    return false;
   }
 
   inline auto
diff --git a/libbuild2/target.txx b/libbuild2/target.txx
index 777653a..d304daa 100644
--- a/libbuild2/target.txx
+++ b/libbuild2/target.txx
@@ -28,11 +28,13 @@ namespace build2
         return;
       }
 
-      if (g_.count != 0) // Skip empty see through groups.
-      {
-        j_ = 1; // Start from the first group member.
+      // Skip empty see through groups.
+      //
+      for (j_ = 1; j_ <= g_.count && g_.members[j_ - 1] == nullptr; ++j_) ;
+      if (j_ <= g_.count)
         break;
-      }
+
+      g_.count = 0;
     }
     while (++i_ != r_->e_ && i_->type.see_through);
   }