From 1bfc71d4dab0a7347f76dc6f0afc1346bd3dc3bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Tue, 8 Apr 2025 23:11:32 +0200
Subject: [PATCH] build: Set LLVM_BUILD_STATIC/CLANG_BUILD_STATIC when linking
 statically.

This is needed since LLVM 20, particularly for Windows.
---
 CMakeLists.txt | 7 +++++++
 build.zig      | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 15f981b069..4bb75bc9cf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -698,6 +698,13 @@ add_library(zigcpp STATIC ${ZIG_CPP_SOURCES})
 target_compile_features(zigcpp PRIVATE cxx_std_17)
 set_target_properties(zigcpp PROPERTIES POSITION_INDEPENDENT_CODE ${ZIG_PIE})
 
+if(LLVM_LINK_MODE STREQUAL "static")
+  target_compile_definitions(zigcpp PRIVATE
+    LLVM_BUILD_STATIC
+    CLANG_BUILD_STATIC
+  )
+endif()
+
 if(NOT MSVC)
   if(MINGW)
     target_compile_options(zigcpp PRIVATE -Wno-format)
diff --git a/build.zig b/build.zig
index 07f781e158..d3fe688f9f 100644
--- a/build.zig
+++ b/build.zig
@@ -706,6 +706,9 @@ const exe_cflags = [_][]const u8{
     "-Wno-type-limits",
     "-Wno-missing-braces",
     "-Wno-comment",
+    // `exe_cflags` is only used for static linking.
+    "-DLLVM_BUILD_STATIC",
+    "-DCLANG_BUILD_STATIC",
 };
 
 fn addCmakeCfgOptionsToExe(