diff options
Diffstat (limited to 'libbuild2/config/utility.cxx')
| -rw-r--r-- | libbuild2/config/utility.cxx | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/libbuild2/config/utility.cxx b/libbuild2/config/utility.cxx index cf0f73b..b3f94be 100644 --- a/libbuild2/config/utility.cxx +++ b/libbuild2/config/utility.cxx @@ -33,9 +33,31 @@ namespace build2 if (var.overrides != nullptr) { - pair<lookup, size_t> ovr (rs.lookup_override (var, move (org))); - - if (l != ovr.first) // Overriden? + // This is tricky: if we didn't find the original, pretend we have set + // the default value for the purpose of override lookup in order to + // have consistent semantics with the default value case (see notes in + // that implementation for background). + // + // In particular, this makes sure we can first do the lookup without + // the default value and then, if there is no value, call the version + // with the default value and end up with the same result if we called + // the default value version straight away. + // + // Note that we need to detect both when the default value is not + // overridden as well as when the override is based on it (e.g., via + // append; think config.cxx+=-m32). + // + // @@ Maybe a callback that computes the default value on demand is a + // better way? + // + variable_map::value_data v; // NULL value, but must be with version. + if (!l.defined ()) + org = make_pair (lookup (v, var, rs), 1); // As default value case. + + scope::override_info li (rs.lookup_override_info (var, move (org))); + pair<lookup, size_t>& ovr (li.lookup); + + if (l.defined () ? l != ovr.first : !li.original) // Overriden? { // Override is always treated as new. // |