From 3cf8015a4941c43ae82100dc0d998945485d760c Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 25 Aug 2020 16:18:58 +0200
Subject: Fix bug in interaction of unmatch logic with target groups

---
 libbuild2/algorithm.cxx |  2 +-
 libbuild2/algorithm.ixx |  9 +++++++--
 libbuild2/operation.cxx | 15 +++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/libbuild2/algorithm.cxx b/libbuild2/algorithm.cxx
index 75540ff..5b340c7 100644
--- a/libbuild2/algorithm.cxx
+++ b/libbuild2/algorithm.cxx
@@ -584,7 +584,7 @@ namespace build2
       else
         l.offset = target::offset_tried;
 
-      return r; // Group state.
+      return r; // Group state (must be consistent with matched_state()).
     }
 
     try
diff --git a/libbuild2/algorithm.ixx b/libbuild2/algorithm.ixx
index 9d77d61..97a8519 100644
--- a/libbuild2/algorithm.ixx
+++ b/libbuild2/algorithm.ixx
@@ -322,12 +322,17 @@ namespace build2
     if (s == target_state::failed)
       throw failed ();
 
+    // If this is a member of the group then the state we've got is that of
+    // the group, not the member, while the member has matched the group and
+    // incremented its dependency counts. As a result, we cannot rely on the
+    // unchanged state in this case.
+    //
     switch (um)
     {
     case unmatch::none: break;
     case unmatch::unchanged:
       {
-        if (s == target_state::unchanged)
+        if (s == target_state::unchanged && t.group == nullptr)
           return make_pair (true, s);
 
         break;
@@ -338,7 +343,7 @@ namespace build2
         // we never decrement this count during match so that someone else
         // cannot change their mind).
         //
-        if (s == target_state::unchanged                   ||
+        if ((s == target_state::unchanged && t.group == nullptr) ||
             t[a].dependents.load (memory_order_consume) != 0)
           return make_pair (true, s);
 
diff --git a/libbuild2/operation.cxx b/libbuild2/operation.cxx
index a14dfb7..1594d8b 100644
--- a/libbuild2/operation.cxx
+++ b/libbuild2/operation.cxx
@@ -442,6 +442,21 @@ namespace build2
     // haven't failed (in which case we could have bailed out early).
     //
     assert (ctx.target_count.load (memory_order_relaxed) == 0);
+
+#ifndef NDEBUG
+    if (ctx.dependency_count.load (memory_order_relaxed) != 0)
+    {
+      diag_record dr;
+      dr << info << "detected unexecuted matched targets:";
+
+      for (const auto& pt: ctx.targets)
+      {
+        const target& t (*pt);
+        if (size_t n = t[a].dependents.load (memory_order_relaxed))
+          dr << text << t << ' ' << n;
+      }
+    }
+#endif
     assert (ctx.dependency_count.load (memory_order_relaxed) == 0);
   }
 
-- 
cgit v1.1