From ed1a0785822e73b910b18a7920be9f58fda67ba8 Mon Sep 17 00:00:00 2001
From: Tim Besard <tim.besard@gmail.com>
Date: Tue, 24 Oct 2023 13:02:56 +0200
Subject: [PATCH] LLVMExtra: Dynamically pick a C++ standard version.

---
 deps/LLVMExtra/CMakeLists.txt | 6 +++++-
 deps/build_local.jl           | 9 ++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/deps/LLVMExtra/CMakeLists.txt b/deps/LLVMExtra/CMakeLists.txt
index 9abcd992..1b9d0198 100644
--- a/deps/LLVMExtra/CMakeLists.txt
+++ b/deps/LLVMExtra/CMakeLists.txt
@@ -13,7 +13,11 @@ LANGUAGES
    C
 )
 
-set(CMAKE_CXX_STANDARD 17)
+if(NOT DEFINED CXX_STANDARD)
+  set(CXX_STANDARD 17)
+endif()
+set(CMAKE_CXX_STANDARD ${CXX_STANDARD})
+
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 
diff --git a/deps/build_local.jl b/deps/build_local.jl
index 032d3619..ca993b94 100644
--- a/deps/build_local.jl
+++ b/deps/build_local.jl
@@ -45,10 +45,17 @@ else
 end
 LLVM_DIR = joinpath(LLVM.artifact_dir, "lib", "cmake", "llvm")
 
+# LLVM 16 requires C++17
+cxx_standard = if Base.libllvm_version >= v"16"
+    "17"
+else
+    "14"
+end
+
 # build and install
 @info "Building" source_dir scratch_dir build_dir LLVM_DIR
 cmake() do cmake_path
-    config_opts = `-DLLVM_ROOT=$(LLVM_DIR) -DCMAKE_INSTALL_PREFIX=$(scratch_dir)`
+    config_opts = `-DLLVM_ROOT=$(LLVM_DIR) -DCXX_STANDARD=$(cxx_standard) -DCMAKE_INSTALL_PREFIX=$(scratch_dir)`
     if Sys.iswindows()
         # prevent picking up MSVC
         config_opts = `$config_opts -G "MSYS Makefiles"`