From 70c6506a7e804127aad176b8ebbb3db951848a5d Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Tue, 7 May 2019 14:06:20 -0400
Subject: [PATCH] src/CMakeLists: Add /Zc:externConstexpr to the MSVC build
 flags

The C++ standard allows constexpr variables declared with the extern
keyword to have external linkage. Previously MSVC wasn't abiding by
this. This just makes the compiler more standards compliant during
builds.

Given we currently don't make use of anything that would break by this,
this is safe to enable.
---
 src/CMakeLists.txt | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 095aadbe8..a1d87bbbc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -21,14 +21,15 @@ if (MSVC)
     # Ensure that projects build with Unicode support.
     add_definitions(-DUNICODE -D_UNICODE)
 
-    # /W3             - Level 3 warnings
-    # /MP             - Multi-threaded compilation
-    # /Zi             - Output debugging information
-    # /Zo             - Enhanced debug info for optimized builds
-    # /permissive-    - Enables stricter C++ standards conformance checks
-    # /EHsc           - C++-only exception handling semantics
-    # /Zc:inline      - Let codegen omit inline functions in object files
-    # /Zc:throwingNew - Let codegen assume `operator new` (without std::nothrow) will never return null
+    # /W3                 - Level 3 warnings
+    # /MP                 - Multi-threaded compilation
+    # /Zi                 - Output debugging information
+    # /Zo                 - Enhanced debug info for optimized builds
+    # /permissive-        - Enables stricter C++ standards conformance checks
+    # /EHsc               - C++-only exception handling semantics
+    # /Zc:externConstexpr - Allow extern constexpr variables to have external linkage, like the standard mandates
+    # /Zc:inline          - Let codegen omit inline functions in object files
+    # /Zc:throwingNew     - Let codegen assume `operator new` (without std::nothrow) will never return null
     add_compile_options(
         /W3
         /MP
@@ -37,6 +38,7 @@ if (MSVC)
         /permissive-
         /EHsc
         /std:c++latest
+        /Zc:externConstexpr
         /Zc:inline
         /Zc:throwingNew
     )