From afead4e749794e6d0f6b9cb9bd7897face64104a Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Thu, 11 May 2017 10:35:45 -0700
Subject: [PATCH] [core] Return {Source,Layer}::getID by value

Avoid dangling references in the following sequence:

    auto& id = layer->getID();
    layer->setMaxZoom(2);
    std::cout << id;

The reference would be dangling because mutating the layer allocates a new Immutable impl, and there may be no references to the prior impl, which held the id.
---
 include/mbgl/style/layer.hpp  | 2 +-
 include/mbgl/style/source.hpp | 2 +-
 src/mbgl/style/layer.cpp      | 2 +-
 src/mbgl/style/source.cpp     | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
index 10176879c..61706d400 100644
--- a/include/mbgl/style/layer.hpp
+++ b/include/mbgl/style/layer.hpp
@@ -92,7 +92,7 @@ public:
     }
 
     LayerType getType() const;
-    const std::string& getID() const;
+    std::string getID() const;
 
     // Visibility
     VisibilityType getVisibility() const;
diff --git a/include/mbgl/style/source.hpp b/include/mbgl/style/source.hpp
index d19dfd4e3..cec961945 100644
--- a/include/mbgl/style/source.hpp
+++ b/include/mbgl/style/source.hpp
@@ -56,7 +56,7 @@ public:
     }
 
     SourceType getType() const;
-    const std::string& getID() const;
+    std::string getID() const;
     optional<std::string> getAttribution() const;
 
     // Private implementation
diff --git a/src/mbgl/style/layer.cpp b/src/mbgl/style/layer.cpp
index fe51dd09c..142fe313c 100644
--- a/src/mbgl/style/layer.cpp
+++ b/src/mbgl/style/layer.cpp
@@ -18,7 +18,7 @@ LayerType Layer::getType() const {
     return baseImpl->type;
 }
 
-const std::string& Layer::getID() const {
+std::string Layer::getID() const {
     return baseImpl->id;
 }
 
diff --git a/src/mbgl/style/source.cpp b/src/mbgl/style/source.cpp
index 4fcebc837..e7701b8be 100644
--- a/src/mbgl/style/source.cpp
+++ b/src/mbgl/style/source.cpp
@@ -19,7 +19,7 @@ SourceType Source::getType() const {
     return baseImpl->type;
 }
 
-const std::string& Source::getID() const {
+std::string Source::getID() const {
     return baseImpl->id;
 }