From 9188bf42b6c8fd34b6d89c8011c950d08488be95 Mon Sep 17 00:00:00 2001
From: Arne Juul <arnej@yahoo-inc.com>
Date: Tue, 9 Oct 2018 07:23:33 +0000
Subject: move empty id to constexpr in header

---
 metrics/src/vespa/metrics/metric.cpp                          | 2 +-
 metrics/src/vespa/metrics/metric.h                            | 2 +-
 staging_vespalib/src/vespa/vespalib/metrics/handle.h          | 3 +++
 staging_vespalib/src/vespa/vespalib/metrics/name_collection.h | 2 ++
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/metrics/src/vespa/metrics/metric.cpp b/metrics/src/vespa/metrics/metric.cpp
index 82f9c848ece..579e3bdfbe3 100644
--- a/metrics/src/vespa/metrics/metric.cpp
+++ b/metrics/src/vespa/metrics/metric.cpp
@@ -44,7 +44,7 @@ vespalib::Regexp Metric::_namePattern(namePattern);
 
 Tag::Tag(vespalib::stringref k)
     : _key(NameRepo::tagKeyId(k)),
-      _value(0)
+      _value(TagValueId::empty_handle)
 { }
 Tag::Tag(vespalib::stringref k, vespalib::stringref v)
     : _key(NameRepo::tagKeyId(k)),
diff --git a/metrics/src/vespa/metrics/metric.h b/metrics/src/vespa/metrics/metric.h
index c92cad8c0cd..d1313c3ca1a 100644
--- a/metrics/src/vespa/metrics/metric.h
+++ b/metrics/src/vespa/metrics/metric.h
@@ -94,7 +94,7 @@ struct Tag
     Tag & operator = (Tag &&) = default;
     ~Tag();
 
-    bool hasValue() const { return _value.id() != 0; }
+    bool hasValue() const { return (_value != TagValueId::empty_handle); }
 
 private:
     TagKeyId _key;
diff --git a/staging_vespalib/src/vespa/vespalib/metrics/handle.h b/staging_vespalib/src/vespa/vespalib/metrics/handle.h
index ddae0b1b6d2..3e32945ceed 100644
--- a/staging_vespalib/src/vespa/vespalib/metrics/handle.h
+++ b/staging_vespalib/src/vespa/vespalib/metrics/handle.h
@@ -15,9 +15,12 @@ template <typename T>
 class Handle {
 private:
     size_t _id;
+    constexpr Handle() : _id(0) {}
 public:
     explicit Handle(size_t id) : _id(id) {}
     size_t id() const { return _id; }
+
+    static constexpr Handle empty_handle = Handle();
 };
 
 template <typename T>
diff --git a/staging_vespalib/src/vespa/vespalib/metrics/name_collection.h b/staging_vespalib/src/vespa/vespalib/metrics/name_collection.h
index 6a91c2d4a9d..6e939cd372d 100644
--- a/staging_vespalib/src/vespa/vespalib/metrics/name_collection.h
+++ b/staging_vespalib/src/vespa/vespalib/metrics/name_collection.h
@@ -23,6 +23,8 @@ public:
 
     NameCollection();
     ~NameCollection() {}
+
+    static constexpr size_t empty_id = 0;
 };
 
 } // namespace vespalib::metrics
-- 
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