Allow ad hoc rules not to list targets that are updated during match

For example, this allows a Qt moc rule not to list generated headers
from libQtCore since they are pre-generated by the library.

3 files changed, 19 insertions, 8 deletions

diff --git a/libbuild2/cc/common.cxx b/libbuild2/cc/common.cxx
index 976127f..a320626 100644
--- a/libbuild2/cc/common.cxx
+++ b/libbuild2/cc/common.cxx
@@ -397,7 +397,9 @@ namespace build2
             {
               // See link_rule for details.
               //
-              const target* g ((pt.include & 4) != 0 ? f->group : nullptr);
+              const target* g ((pt.include & include_group) != 0
+                               ? f->group
+                               : nullptr);
 
               if (sysd == nullptr) find_sysd ();
               if (!li) find_linfo ();
diff --git a/libbuild2/cc/common.hxx b/libbuild2/cc/common.hxx
index a5a4859..2aaa0d0 100644
--- a/libbuild2/cc/common.hxx
+++ b/libbuild2/cc/common.hxx
@@ -305,6 +305,11 @@ namespace build2
 
       using library_cache = small_vector<library_cache_entry, 32>;
 
+      // The prerequisite_target::include bit that indicates a library
+      // member has been picked from the group.
+      //
+      static const uintptr_t include_group = 0x100;
+
       void
       process_libraries (
         action,
diff --git a/libbuild2/cc/link-rule.cxx b/libbuild2/cc/link-rule.cxx
index 0081fe2..d0a1f4a 100644
--- a/libbuild2/cc/link-rule.cxx
+++ b/libbuild2/cc/link-rule.cxx
@@ -1003,7 +1003,7 @@ namespace build2
             if (*um)
             {
               pto.target = &p.search (t); // mark 0
-              pto.include |= 2;
+              pto.include |= prerequisite_target::include_udm;
               update_match = true;
             }
           }
@@ -1144,7 +1144,7 @@ namespace build2
           if (const libx* l = pt->is_a<libx> ())
           {
             pt = link_member (*l, a, li);
-            pto.include |= 4;
+            pto.include |= include_group;
           }
         }
         else
@@ -1231,7 +1231,7 @@ namespace build2
                    << "not supported by this rule";
 
             m = 0;
-            pto.include |= 2;
+            pto.include |= prerequisite_target::include_udm;
             update_match = true;
           }
         }
@@ -1245,10 +1245,14 @@ namespace build2
       // of the libraries (for example, if generation requires some of the
       // metadata; think poptions needed by Qt moc).
       //
-      match_members (a, t, pts, start, {2 /* mask */, 0 /* value */});
+      {
+        auto mask (prerequisite_target::include_udm);
 
-      if (update_match)
-        match_members (a, t, pts, start, {2, 2});
+        match_members (a, t, pts, start, {mask, 0});
+
+        if (update_match)
+          match_members (a, t, pts, start, {mask, mask});
+      }
 
       // Check if we have any binful utility libraries.
       //
@@ -1383,7 +1387,7 @@ namespace build2
       // prerequisite_target::data.
       //
       if (update_match)
-        update_during_match_prerequisites (trace, a, t, 2 /* mask */);
+        update_during_match_prerequisites (trace, a, t);
 
       // Now that we know for sure whether we are binless, derive file name(s)
       // and add ad hoc group members. Note that for binless we still need the