Tighten value::extra usage in config module

Specifically, only values marked with 1 are treated as default leaving
other values for use for other purposes.

4 files changed, 10 insertions, 5 deletions

diff --git a/libbuild2/config/operation.cxx b/libbuild2/config/operation.cxx
index ed98f90..5edb610 100644
--- a/libbuild2/config/operation.cxx
+++ b/libbuild2/config/operation.cxx
@@ -509,8 +509,8 @@ namespace build2
 
             // Handle the save_default_commented flag.
             //
-            if ((org.first.defined () && org.first->extra) && // Default value.
-                org.first == ovr.first &&                     // Not overriden.
+            if (org.first.defined () && org.first->extra == 1 && // Default.
+                org.first == ovr.first &&                        // No override.
                 (flags & save_default_commented) != 0)
             {
               os << first () << '#' << n << " =" << endl;
diff --git a/libbuild2/config/utility.cxx b/libbuild2/config/utility.cxx
index a64d4d5..2ce94ff 100644
--- a/libbuild2/config/utility.cxx
+++ b/libbuild2/config/utility.cxx
@@ -32,7 +32,7 @@ namespace build2
 
       // Treat an inherited value that was set to default as new.
       //
-      if (l.defined () && l->extra)
+      if (l.defined () && l->extra == 1)
         n = true;
 
       if (var.overrides != nullptr)
@@ -200,7 +200,7 @@ namespace build2
       if (org.first != ovr.first)
         return make_pair (variable_origin::override_, ovr.first);
 
-      return make_pair (org.first->extra
+      return make_pair (org.first->extra == 1
                         ? variable_origin::default_
                         : variable_origin::buildfile,
                         org.first);
diff --git a/libbuild2/config/utility.hxx b/libbuild2/config/utility.hxx
index 1e33568..72fe520 100644
--- a/libbuild2/config/utility.hxx
+++ b/libbuild2/config/utility.hxx
@@ -64,6 +64,11 @@ namespace build2
     // omitted value(s) is the default (see a note in lookup_config()
     // documentation for details).
     //
+    // The below lookup_*() functions mark the default value by setting
+    // value::extra to 1. Note that it's exactly 1 and not "not 0" since other
+    // values could have other meaning (see, for example, package skeleton
+    // in bpkg).
+    //
     const uint64_t save_default_commented = 0x01; // Based on value::extra.
     const uint64_t save_null_omitted      = 0x02; // Treat NULL as undefined.
     const uint64_t save_empty_omitted     = 0x04; // Treat empty as undefined.
diff --git a/libbuild2/config/utility.txx b/libbuild2/config/utility.txx
index 0362d6a..71e41fd 100644
--- a/libbuild2/config/utility.txx
+++ b/libbuild2/config/utility.txx
@@ -66,7 +66,7 @@ namespace build2
       }
       // Treat an inherited value that was set to default as new.
       //
-      else if (l->extra)
+      else if (l->extra == 1)
         n = (sflags & save_default_commented) == 0; // Absence means default.
 
       if (var.overrides != nullptr)