From a4d918fa119c9beb712bf08bbb8fa9996aab0a71 Mon Sep 17 00:00:00 2001
From: Carlo Cabrera <github@carlo.cab>
Date: Fri, 13 Dec 2024 03:42:56 +0800
Subject: [PATCH] Replace `DEFAULT_SYSROOT` usage with Clang config files
 (#503)

Upstream want to deprecate `DEFAULT_SYSROOT`[^1][^2][^3], but one
blocker is wasi-sdk's usage of it.

Let's try to help that along by switching to using config files[^4]
instead.

This should result in no user-facing changes in functionality. (If it
does, then that's an LLVM bug that should be fixed there.)

[^1]: https://reviews.llvm.org/D158218
[^2]: https://github.com/llvm/llvm-project/issues/94284
[^3]: https://github.com/llvm/llvm-project/pull/77537
[^4]: https://clang.llvm.org/docs/UsersManual.html#configuration-files
---
 clang.cfg                      |  1 +
 cmake/wasi-sdk-toolchain.cmake | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 clang.cfg

diff --git a/clang.cfg b/clang.cfg
new file mode 100644
index 0000000..38ddf54
--- /dev/null
+++ b/clang.cfg
@@ -0,0 +1 @@
+--sysroot=<CFGDIR>/../share/wasi-sysroot
diff --git a/cmake/wasi-sdk-toolchain.cmake b/cmake/wasi-sdk-toolchain.cmake
index 4c45abf..cba9c63 100644
--- a/cmake/wasi-sdk-toolchain.cmake
+++ b/cmake/wasi-sdk-toolchain.cmake
@@ -90,7 +90,6 @@ ExternalProject_Add(llvm-build
     -DLLVM_DEFAULT_TARGET_TRIPLE=wasm32-wasi
     -DLLVM_INSTALL_BINUTILS_SYMLINKS=TRUE
     -DLLVM_ENABLE_LIBXML2=OFF
-    -DDEFAULT_SYSROOT=../share/wasi-sysroot
     # Pass `-s` to strip symbols by default and shrink the size of the
     # distribution
     -DCMAKE_EXE_LINKER_FLAGS=-s
@@ -159,6 +158,18 @@ copy_misc_file(wasi-sdk-p1.cmake cmake)
 copy_misc_file(wasi-sdk-p2.cmake cmake)
 copy_misc_file(cmake/Platform/WASI.cmake cmake/Platform)
 
+function(copy_cfg_file compiler)
+  set(dst ${wasi_tmp_install}/bin/${compiler}.cfg)
+  add_custom_command(
+    OUTPUT ${dst}
+    COMMAND cmake -E copy ${CMAKE_CURRENT_SOURCE_DIR}/clang.cfg ${dst})
+  add_custom_target(copy-${compiler} DEPENDS ${dst})
+  add_dependencies(misc-files copy-${compiler})
+endfunction()
+
+copy_cfg_file(clang)
+copy_cfg_file(clang++)
+
 include(wasi-sdk-dist)
 
 # Figure out the name of the artifact which is either explicitly specified or