7 files changed, 32 insertions, 18 deletions
diff --git a/include/mbgl/map/mode.hpp b/include/mbgl/map/mode.hpp
index afec5c0a08..05de2df22c 100644
--- a/include/mbgl/map/mode.hpp
+++ b/include/mbgl/map/mode.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <mbgl/util/util.hpp>
 #include <mbgl/util/traits.hpp>
 
 #include <cstdint>
@@ -51,23 +52,23 @@ enum class MapDebugOptions : EnumType {
 #endif // MBGL_USE_GLES2
 };
 
-constexpr MapDebugOptions operator|(MapDebugOptions lhs, MapDebugOptions rhs) {
+MBGL_CONSTEXPR MapDebugOptions operator|(MapDebugOptions lhs, MapDebugOptions rhs) {
     return MapDebugOptions(mbgl::underlying_type(lhs) | mbgl::underlying_type(rhs));
 }
 
-constexpr MapDebugOptions& operator|=(MapDebugOptions& lhs, MapDebugOptions rhs) {
+MBGL_CONSTEXPR MapDebugOptions& operator|=(MapDebugOptions& lhs, MapDebugOptions rhs) {
     return (lhs = MapDebugOptions(mbgl::underlying_type(lhs) | mbgl::underlying_type(rhs)));
 }
 
-constexpr bool operator&(MapDebugOptions lhs, MapDebugOptions rhs) {
+MBGL_CONSTEXPR bool operator&(MapDebugOptions lhs, MapDebugOptions rhs) {
     return mbgl::underlying_type(lhs) & mbgl::underlying_type(rhs);
 }
 
-constexpr MapDebugOptions& operator&=(MapDebugOptions& lhs, MapDebugOptions rhs) {
+MBGL_CONSTEXPR MapDebugOptions& operator&=(MapDebugOptions& lhs, MapDebugOptions rhs) {
     return (lhs = MapDebugOptions(mbgl::underlying_type(lhs) & mbgl::underlying_type(rhs)));
 }
 
-constexpr MapDebugOptions operator~(MapDebugOptions value) {
+MBGL_CONSTEXPR MapDebugOptions operator~(MapDebugOptions value) {
     return MapDebugOptions(~mbgl::underlying_type(value));
 }
 
diff --git a/include/mbgl/util/convert.hpp b/include/mbgl/util/convert.hpp
index c2b3d9950d..bedb1a4a08 100644
--- a/include/mbgl/util/convert.hpp
+++ b/include/mbgl/util/convert.hpp
@@ -1,3 +1,5 @@
+#include <mbgl/util/util.hpp>
+
 #include <array>
 #include <type_traits>
 #include <utility>
@@ -7,7 +9,7 @@ namespace util {
 
 template<typename To, typename From, std::size_t Size,
          typename = std::enable_if_t<std::is_convertible<From, To>::value>>
-constexpr std::array<To, Size> convert(const std::array<From, Size>&from) {
+MBGL_CONSTEXPR std::array<To, Size> convert(const std::array<From, Size>&from) {
     std::array<To, Size> to {};
     std::copy(std::begin(from), std::end(from), std::begin(to));
     return to;
diff --git a/include/mbgl/util/util.hpp b/include/mbgl/util/util.hpp
index c5a7cb3780..7960b40299 100644
--- a/include/mbgl/util/util.hpp
+++ b/include/mbgl/util/util.hpp
@@ -12,3 +12,10 @@
 #define MBGL_VERIFY_THREAD(tid)
 
 #endif
+
+// GCC 4.9 compatibility
+#if !defined(__GNUC__) || __GNUC__ >= 5
+#define MBGL_CONSTEXPR constexpr
+#else
+#define MBGL_CONSTEXPR inline
+#endif
diff --git a/src/mbgl/gl/gl.cpp b/src/mbgl/gl/gl.cpp
index 8999468dbd..bd6d7b192d 100644
--- a/src/mbgl/gl/gl.cpp
+++ b/src/mbgl/gl/gl.cpp
@@ -1,12 +1,13 @@
 #include <mbgl/gl/gl.hpp>
 #include <mbgl/util/string.hpp>
+#include <mbgl/util/util.hpp>
 
 namespace mbgl {
 namespace gl {
 
 namespace {
 
-constexpr const char* stringFromError(GLenum err) {
+MBGL_CONSTEXPR const char* stringFromError(GLenum err) {
     switch (err) {
     case GL_INVALID_ENUM:
         return "GL_INVALID_ENUM";
diff --git a/src/mbgl/map/update.hpp b/src/mbgl/map/update.hpp
index 82d98284f5..ab8b10c651 100644
--- a/src/mbgl/map/update.hpp
+++ b/src/mbgl/map/update.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <mbgl/util/traits.hpp>
+#include <mbgl/util/util.hpp>
 
 namespace mbgl {
 
@@ -11,15 +12,15 @@ enum class Update {
     AnnotationData            = 1 << 7
 };
 
-constexpr Update operator|(Update lhs, Update rhs) {
+MBGL_CONSTEXPR Update operator|(Update lhs, Update rhs) {
     return Update(mbgl::underlying_type(lhs) | mbgl::underlying_type(rhs));
 }
 
-constexpr Update& operator|=(Update& lhs, const Update& rhs) {
+MBGL_CONSTEXPR Update& operator|=(Update& lhs, const Update& rhs) {
     return (lhs = lhs | rhs);
 }
 
-constexpr bool operator& (Update lhs, Update rhs) {
+MBGL_CONSTEXPR bool operator& (Update lhs, Update rhs) {
     return mbgl::underlying_type(lhs) & mbgl::underlying_type(rhs);
 }
 
diff --git a/src/mbgl/renderer/render_pass.hpp b/src/mbgl/renderer/render_pass.hpp
index d273e34ff7..ae2b923ba1 100644
--- a/src/mbgl/renderer/render_pass.hpp
+++ b/src/mbgl/renderer/render_pass.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <mbgl/util/traits.hpp>
+#include <mbgl/util/util.hpp>
 
 #include <cstdint>
 
@@ -12,15 +13,15 @@ enum class RenderPass : uint8_t {
     Translucent = 1 << 1,
 };
 
-constexpr RenderPass operator|(RenderPass a, RenderPass b) {
+MBGL_CONSTEXPR RenderPass operator|(RenderPass a, RenderPass b) {
     return RenderPass(mbgl::underlying_type(a) | mbgl::underlying_type(b));
 }
 
-constexpr RenderPass& operator|=(RenderPass& a, RenderPass b) {
+MBGL_CONSTEXPR RenderPass& operator|=(RenderPass& a, RenderPass b) {
     return (a = a | b);
 }
 
-constexpr RenderPass operator&(RenderPass a, RenderPass b) {
+MBGL_CONSTEXPR RenderPass operator&(RenderPass a, RenderPass b) {
     return RenderPass(mbgl::underlying_type(a) & mbgl::underlying_type(b));
 }
 
diff --git a/src/mbgl/text/glyph.hpp b/src/mbgl/text/glyph.hpp
index b9eaedd302..19ecdfd17c 100644
--- a/src/mbgl/text/glyph.hpp
+++ b/src/mbgl/text/glyph.hpp
@@ -7,6 +7,7 @@
 #include <mbgl/util/optional.hpp>
 #include <mbgl/util/immutable.hpp>
 #include <mbgl/util/image.hpp>
+#include <mbgl/util/util.hpp>
 
 #include <cstdint>
 #include <vector>
@@ -89,23 +90,23 @@ enum class WritingModeType : uint8_t {
     Vertical = 1 << 1,
 };
 
-constexpr WritingModeType operator|(WritingModeType a, WritingModeType b) {
+MBGL_CONSTEXPR WritingModeType operator|(WritingModeType a, WritingModeType b) {
     return WritingModeType(mbgl::underlying_type(a) | mbgl::underlying_type(b));
 }
 
-constexpr WritingModeType& operator|=(WritingModeType& a, WritingModeType b) {
+MBGL_CONSTEXPR WritingModeType& operator|=(WritingModeType& a, WritingModeType b) {
     return (a = a | b);
 }
 
-constexpr bool operator&(WritingModeType lhs, WritingModeType rhs) {
+MBGL_CONSTEXPR bool operator&(WritingModeType lhs, WritingModeType rhs) {
     return mbgl::underlying_type(lhs) & mbgl::underlying_type(rhs);
 }
 
-constexpr WritingModeType& operator&=(WritingModeType& lhs, WritingModeType rhs) {
+MBGL_CONSTEXPR WritingModeType& operator&=(WritingModeType& lhs, WritingModeType rhs) {
     return (lhs = WritingModeType(mbgl::underlying_type(lhs) & mbgl::underlying_type(rhs)));
 }
 
-constexpr WritingModeType operator~(WritingModeType value) {
+MBGL_CONSTEXPR WritingModeType operator~(WritingModeType value) {
     return WritingModeType(~mbgl::underlying_type(value));
 }