@@ 0,0 1,96 @@
+Clang attempts to guess file names based on the OS and distro (yes!),
+but unfortunately, that doesn't work for us.
+
+This patch makes it easy to insert libc's $libdir so that Clang passes the
+correct absolute file name of crt1.o etc. to 'ld'.  It also disables all
+the distro-specific stuff and removes the hard-coded FHS directory names
+to make sure Clang also works on foreign distros.
+
+diff --git a/clang/lib/Driver/Distro.cpp b/clang/lib/Driver/Distro.cpp
+index ee4fe841..f0313bbe 100644
+--- a/clang/lib/Driver/Distro.cpp
++++ b/clang/lib/Driver/Distro.cpp
+@@ -93,6 +93,10 @@ static Distro::DistroType DetectLsbRelease(llvm::vfs::FileSystem &VFS) {
+ }
+ 
+ static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS) {
++  // The compiler should always behave the same, even when used via Guix on a
++  // foreign distro.
++  return Distro::UnknownDistro;
++
+   Distro::DistroType Version = Distro::UnknownDistro;
+ 
+   // Newer freedesktop.org's compilant systemd-based systems
+diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp b/clang/lib/Driver/ToolChains/Cuda.cpp
+index d14776c5..88bc3ccd 100644
+--- a/clang/lib/Driver/ToolChains/Cuda.cpp
++++ b/clang/lib/Driver/ToolChains/Cuda.cpp
+@@ -119,6 +119,9 @@ CudaInstallationDetector::CudaInstallationDetector(
+     const Driver &D, const llvm::Triple &HostTriple,
+     const llvm::opt::ArgList &Args)
+     : D(D) {
++  // Don't look for CUDA in /usr.
++  return;
++
+   struct Candidate {
+     std::string Path;
+     bool StrictChecking;
+diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
+--- a/clang/lib/Driver/ToolChains/Linux.cpp
++++ b/clang/lib/Driver/ToolChains/Linux.cpp
+@@ -186,6 +186,10 @@
+ 
+   Generic_GCC::PushPPaths(PPaths);
+ 
++  // Comment out the distro-specific tweaks so that they don't bite when
++  // using Guix on a foreign distro.
++#if 0
++
+   Distro Distro(D.getVFS(), Triple);
+ 
+   if (Distro.IsAlpineLinux() || Triple.isAndroid()) {
+@@ -251,6 +255,7 @@
+ 
+   if (IsAndroid || Distro.IsOpenSUSE())
+     ExtraOpts.push_back("--enable-new-dtags");
++#endif
+ 
+   // The selection of paths to try here is designed to match the patterns which
+   // the GCC driver itself uses, as this is part of the GCC-compatible driver.
+@@ -264,6 +269,7 @@
+ 
+   Generic_GCC::AddMultilibPaths(D, SysRoot, OSLibDir, MultiarchTriple, Paths);
+ 
++#if 0
+   addPathIfExists(D, SysRoot + "/lib/" + MultiarchTriple, Paths);
+   addPathIfExists(D, SysRoot + "/lib/../" + OSLibDir, Paths);
+ 
+@@ -295,9 +301,11 @@
+     addPathIfExists(D, SysRoot + "/" + OSLibDir + "/" + ABIName, Paths);
+     addPathIfExists(D, SysRoot + "/usr/" + OSLibDir + "/" + ABIName, Paths);
+   }
++#endif
+ 
+   Generic_GCC::AddMultiarchPaths(D, SysRoot, OSLibDir, Paths);
+ 
++#if 0
+   // Similar to the logic for GCC above, if we are currently running Clang
+   // inside of the requested system root, add its parent library path to those
+   // searched.
+@@ -305,9 +313,14 @@
+   // directory ('Dir' below) or the ResourceDir.
+   if (StringRef(D.Dir).startswith(SysRoot))
+     addPathIfExists(D, D.Dir + "/../lib", Paths);
++#endif
++
++  // Add libc's lib/ directory to the search path, so that crt1.o, crti.o,
++  // and friends can be found.
++  addPathIfExists(D, "@GLIBC_LIBDIR@", Paths);
+ 
+-  addPathIfExists(D, SysRoot + "/lib", Paths);
+-  addPathIfExists(D, SysRoot + "/usr/lib", Paths);
++  // Add GCC's lib/ directory so libstdc++.so can be found.
++  addPathIfExists(D, GCCInstallation.getParentLibPath(), Paths);
+ }
+ 
+ ToolChain::RuntimeLibType Linux::GetDefaultRuntimeLibType() const {


@@ 1,329 1,107 @@
-From 811f0a575231496318b5e9c9a0ff0ed195b16dc0 Mon Sep 17 00:00:00 2001
-From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
-Date: Tue, 7 Sep 2021 16:35:07 -0400
-Subject: [PATCH] build: Allow building Cling using the Clang shared library.
+Upstream status: https://github.com/root-project/root/pull/15563
 
-The officially supported way to build LLVM/Clang as a shared library
-is via the LLVM_BUILD_LLVM_DYLIB and LLVM_LINK_LLVM_DYLIB CMake
-options (see: https://llvm.org/docs/BuildingADistribution.html).  When
-built this way, the whole of Clang API is exposed as a shared
-library (libclang-cpp.so).
-
-* CMakeLists.txt: Query if we're in shared mode via llvm-config, and
-register the result as LLVM_LIB_IS_SHARED.
-[LLVM_LIB_IS_SHARED] <target_link_libraries>: Use the PUBLIC interface of the
-LLVM shared library.
-* lib/Interpreter/CMakeLists.txt [LLVM_LIB_IS_SHARED]: When defined, replace the
-individual Clang components by clang-cpp.
-* lib/MetaProcessor/CMakeLists.txt: Likewise.
-* lib/Utils/CMakeLists.txt: Likewise.
-* tools/Jupyter/CMakeLists.txt: Likewise.
-* tools/driver/CMakeLists.txt: Likewise.
-* tools/libcling/CMakeLists.txt: Likewise.
----
- CMakeLists.txt                   | 10 ++++++--
- lib/Interpreter/CMakeLists.txt   | 40 ++++++++++++++++++--------------
- lib/MetaProcessor/CMakeLists.txt | 16 +++++++++----
- lib/Utils/CMakeLists.txt         | 34 +++++++++++++++------------
- tools/Jupyter/CMakeLists.txt     | 11 ++++++++-
- tools/driver/CMakeLists.txt      | 16 +++----------
- tools/libcling/CMakeLists.txt    | 38 +++++++++++++++---------------
- 7 files changed, 93 insertions(+), 72 deletions(-)
-
-diff --git a/CMakeLists.txt b/CMakeLists.txt
-index 65b14b27..888f7ee9 100644
+diff --git a/interpreter/cling/CMakeLists.txt b/interpreter/cling/CMakeLists.txt
+index 9775b07f10..7028042096 100644
 --- a/CMakeLists.txt
 +++ b/CMakeLists.txt
-@@ -23,6 +23,7 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
-       "--libdir"
-       "--includedir"
-       "--prefix"
-+      "--shared-mode"
-       "--src-root")
-     execute_process(
-       COMMAND ${CONFIG_COMMAND}
-@@ -47,7 +48,8 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
-   list(GET CONFIG_OUTPUT 2 LIBRARY_DIR)
-   list(GET CONFIG_OUTPUT 3 INCLUDE_DIR)
-   list(GET CONFIG_OUTPUT 4 LLVM_OBJ_ROOT)
--  list(GET CONFIG_OUTPUT 5 MAIN_SRC_DIR)
-+  list(GET CONFIG_OUTPUT 5 LLVM_LIB_IS_SHARED)
-+  list(GET CONFIG_OUTPUT 6 MAIN_SRC_DIR)
- 
-   if(NOT MSVC_IDE)
-     set(LLVM_ENABLE_ASSERTIONS ${ENABLE_ASSERTIONS}
-@@ -427,7 +429,11 @@ macro(add_cling_library name)
-   endif()
- 
-   if(TARGET ${name})
--    target_link_libraries(${name} INTERFACE ${LLVM_COMMON_LIBS})
-+      if(LLVM_LIB_IS_SHARED)
-+          target_link_libraries(${name} PUBLIC LLVM)
-+      else()
-+          target_link_libraries(${name} INTERFACE ${LLVM_COMMON_LIBS})
-+      endif()
- 
-     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "libcling")
-       install(TARGETS ${name}
-diff --git a/lib/Interpreter/CMakeLists.txt b/lib/Interpreter/CMakeLists.txt
-index 921c773c..af65c020 100644
---- a/lib/Interpreter/CMakeLists.txt
-+++ b/lib/Interpreter/CMakeLists.txt
-@@ -6,22 +6,28 @@
- # LICENSE.TXT for details.
- #------------------------------------------------------------------------------
- 
--set(LIBS
--  clingUtils
--  clangCodeGen
--  clangDriver
--  clangFrontend
--  clangParse
--  clangSema
--  clangAnalysis
--  clangEdit
--  clangRewrite
--  clangRewriteFrontend
--  clangSerialization
--  clangAST
--  clangBasic
--  clangLex
--)
-+if (LLVM_LIB_IS_SHARED)
-+    set(LIBS
-+        clang-cpp
-+        clingUtils)
-+else()
-+    set(LIBS
-+        clingUtils
-+        clangCodeGen
-+        clangDriver
-+        clangFrontend
-+        clangParse
-+        clangSema
-+        clangAnalysis
-+        clangEdit
-+        clangRewrite
-+        clangRewriteFrontend
-+        clangSerialization
-+        clangAST
-+        clangBasic
-+        clangLex
-+        )
-+endif()
- 
- set(LLVM_LINK_COMPONENTS
-   analysis
-@@ -369,4 +375,4 @@ if ((NOT builtin_llvm) AND builtin_clang)
-   get_property(P SOURCE TransactionUnloader.cpp PROPERTY INCLUDE_DIRECTORIES)
-   list(INSERT P 0 ${FixInclude})
-   set_property(SOURCE TransactionUnloader.cpp PROPERTY INCLUDE_DIRECTORIES "${P}")
--endif()
-\ No newline at end of file
-+endif()
-diff --git a/lib/MetaProcessor/CMakeLists.txt b/lib/MetaProcessor/CMakeLists.txt
-index e753dca3..5f4641bb 100644
---- a/lib/MetaProcessor/CMakeLists.txt
-+++ b/lib/MetaProcessor/CMakeLists.txt
-@@ -10,7 +10,16 @@ set( LLVM_LINK_COMPONENTS
-   core
-   support
-   binaryformat
--)
-+  )
-+
-+if (LLVM_LIB_IS_SHARED)
-+    set(LIBS clang-cpp)
-+else()
-+    set(LIBS
-+        clangLex
-+        clangAST
-+        clangBasic)
-+endif()
- 
- add_cling_library(clingMetaProcessor OBJECT
-   Display.cpp
-@@ -21,10 +30,7 @@ add_cling_library(clingMetaProcessor OBJECT
-   MetaSema.cpp
- 
-   LINK_LIBS
--  clangLex
--  clangAST
--  clangBasic
--
-+  ${LIBS}
-   clingInterpreter
-   clingUtils
- )
-diff --git a/lib/Utils/CMakeLists.txt b/lib/Utils/CMakeLists.txt
-index 327c9fff..fbe4bd87 100644
---- a/lib/Utils/CMakeLists.txt
-+++ b/lib/Utils/CMakeLists.txt
-@@ -26,21 +26,25 @@ set(LLVM_LINK_COMPONENTS
-   ${LLVM_TARGETS_TO_BUILD}
- )
- 
--set(LIBS
--  clangCodeGen
--  clangDriver
--  clangFrontend
--  clangParse
--  clangSema
--  clangAnalysis
--  clangEdit
--  clangRewrite
--  clangRewriteFrontend
--  clangSerialization
--  clangAST
--  clangBasic
--  clangLex
--)
-+if (LLVM_LIB_IS_SHARED)
-+    set(LIBS clang-cpp)
-+else()
-+    set(LIBS
-+        clangCodeGen
-+        clangDriver
-+        clangFrontend
-+        clangParse
-+        clangSema
-+        clangAnalysis
-+        clangEdit
-+        clangRewrite
-+        clangRewriteFrontend
-+        clangSerialization
-+        clangAST
-+        clangBasic
-+        clangLex
-+        )
-+endif()
- 
- find_library(DL_LIBRARY_PATH dl)
- if (DL_LIBRARY_PATH)
-diff --git a/tools/Jupyter/CMakeLists.txt b/tools/Jupyter/CMakeLists.txt
-index aad5f3f7..8b4ac36f 100644
---- a/tools/Jupyter/CMakeLists.txt
-+++ b/tools/Jupyter/CMakeLists.txt
-@@ -39,6 +39,14 @@ else()
-    endif()
- endif()
- 
-+if (LLVM_LIB_IS_SHARED)
-+    set(LIBS
-+        clang-cpp
-+        clingUserInterface
-+        clingMetaProcessor
-+        ${INTERPRETER}
-+        clingUtils)
-+else()
- set(LIBS
-         clangAST
-         clangBasic
-@@ -54,7 +62,8 @@ set(LIBS
-         clingMetaProcessor
-         ${INTERPRETER}
-         clingUtils
+@@ -13,81 +13,22 @@ endif(WIN32)
+ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
+   project(Cling)
+ 
+-  # Rely on llvm-config.
+-  set(CONFIG_OUTPUT)
+-  find_program(LLVM_CONFIG "llvm-config")
+-  if(LLVM_CONFIG)
+-    message(STATUS "Found LLVM_CONFIG as ${LLVM_CONFIG}")
+-    set(CONFIG_COMMAND ${LLVM_CONFIG}
+-      "--assertion-mode"
+-      "--bindir"
+-      "--libdir"
+-      "--includedir"
+-      "--prefix")
+-    execute_process(
+-      COMMAND ${CONFIG_COMMAND}
+-      RESULT_VARIABLE HAD_ERROR
+-      OUTPUT_VARIABLE CONFIG_OUTPUT
 -    )
-+        )
-+endif()
- 
- if( LLVM_ENABLE_PIC )
-     set(ENABLE_SHARED SHARED)
-diff --git a/tools/driver/CMakeLists.txt b/tools/driver/CMakeLists.txt
-index 1968b97f..5ed53fb7 100644
---- a/tools/driver/CMakeLists.txt
-+++ b/tools/driver/CMakeLists.txt
-@@ -9,23 +9,13 @@
- # Keep symbols for JIT resolution
- set(LLVM_NO_DEAD_STRIP 1)
- 
--if(BUILD_SHARED_LIBS)
--  set(LIBS
--    LLVMSupport
+-    if(NOT HAD_ERROR)
+-      string(REGEX REPLACE
+-        "[ \t]*[\r\n]+[ \t]*" ";"
+-        CONFIG_OUTPUT ${CONFIG_OUTPUT})
+-    else()
+-      string(REPLACE ";" " " CONFIG_COMMAND_STR "${CONFIG_COMMAND}")
+-      message(STATUS "${CONFIG_COMMAND_STR}")
+-      message(FATAL_ERROR "llvm-config failed with status ${HAD_ERROR}")
+-    endif()
+-  else()
+-    message(FATAL_ERROR "llvm-config not found -- ${LLVM_CONFIG}")
+-  endif()
++  # See <https://llvm.org/docs/CMake.html#embedding-llvm-in-your-project>.
++  find_package(LLVM REQUIRED CONFIG)
++  message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
++  message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
+ 
+-  list(GET CONFIG_OUTPUT 0 ENABLE_ASSERTIONS)
+-  list(GET CONFIG_OUTPUT 1 TOOLS_BINARY_DIR)
+-  list(GET CONFIG_OUTPUT 2 LIBRARY_DIR)
+-  list(GET CONFIG_OUTPUT 3 INCLUDE_DIR)
+-  list(GET CONFIG_OUTPUT 4 LLVM_OBJ_ROOT)
 -
--    clangFrontendTool
+-  if(NOT MSVC_IDE)
+-    set(LLVM_ENABLE_ASSERTIONS ${ENABLE_ASSERTIONS}
+-      CACHE BOOL "Enable assertions")
+-    # Assertions should follow llvm-config's.
+-    mark_as_advanced(LLVM_ENABLE_ASSERTIONS)
+-  endif()
++  separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
++  add_definitions(${LLVM_DEFINITIONS_LIST})
+ 
+-  set(LLVM_TOOLS_BINARY_DIR ${TOOLS_BINARY_DIR} CACHE PATH "Path to llvm/bin")
+-  set(LLVM_LIBRARY_DIR ${LIBRARY_DIR} CACHE PATH "Path to llvm/lib")
+-  set(LLVM_MAIN_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
+-  set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
++  find_package(Clang REQUIRED CONFIG)
++  message(STATUS "Found supported version: Clang ${CLANG_PACKAGE_VERSION}")
++  message(STATUS "Using ClangConfig.cmake in: ${Clang_DIR}")
+ 
+   find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR}
+     NO_DEFAULT_PATH)
+ 
+-  set(LLVM_CMAKE_PATH "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
+-  set(LLVMCONFIG_FILE "${LLVM_CMAKE_PATH}/LLVMConfig.cmake")
+-  if(EXISTS ${LLVMCONFIG_FILE})
+-    list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")
+-    include(${LLVMCONFIG_FILE})
+-  else()
+-    message(FATAL_ERROR "Not found: ${LLVMCONFIG_FILE}")
+-  endif()
 -
--    clingInterpreter
--    clingMetaProcessor
--    clingUserInterface
--    clingUtils
--  )
-+if(LLVM_LIB_IS_SHARED)
-+  set(LIBS clang-cpp clingUserInterface)
-   add_cling_executable(cling
-     cling.cpp
-   )
- else()
-   set(LIBS
--    LLVMSupport
- 
-     clangASTMatchers
-     clangFrontendTool
-@@ -38,7 +28,7 @@ else()
-     $<TARGET_OBJECTS:obj.clingMetaProcessor>
-     $<TARGET_OBJECTS:obj.clingUtils>
-   )
--endif(BUILD_SHARED_LIBS)
-+endif(LLVM_LIB_IS_SHARED)
- 
- set_target_properties(cling
-   PROPERTIES ENABLE_EXPORTS 1)
-diff --git a/tools/libcling/CMakeLists.txt b/tools/libcling/CMakeLists.txt
-index 143d3bdb..ba000d44 100644
---- a/tools/libcling/CMakeLists.txt
-+++ b/tools/libcling/CMakeLists.txt
-@@ -10,21 +10,25 @@ set(SOURCES
-   ADDITIONAL_HEADERS
-   )
- 
--set(LIBS
--  clangAnalysis
--  clangDriver
--  clangFrontend
--  clangParse
--  clangSema
--  clangAST
--  clangLex
--  clangSerialization
--  clangCodeGen
--  clangBasic
--  clangEdit
+-  # They are used as destination of target generators.
+-  set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin)
+-  set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
+-  if(WIN32 OR CYGWIN)
+-    # DLL platform -- put DLLs into bin.
+-    set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_RUNTIME_OUTPUT_INTDIR})
+-  else()
+-    set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
+-  endif()
+-
+-  option(LLVM_INSTALL_TOOLCHAIN_ONLY
+-    "Only include toolchain files in the 'install' target." OFF)
+-
+-  option(LLVM_FORCE_USE_OLD_HOST_TOOLCHAIN
+-    "Set to ON to force using an old, unsupported host toolchain." OFF)
 -
--  clingUtils
--)
-+if (LLVM_LIB_IS_SHARED)
-+    set(LIBS clang-cpp)
-+else()
-+    set(LIBS
-+        clangAnalysis
-+        clangDriver
-+        clangFrontend
-+        clangParse
-+        clangSema
-+        clangAST
-+        clangLex
-+        clangSerialization
-+        clangCodeGen
-+        clangBasic
-+        clangEdit
-+
-+        clingUtils
-+        )
-+endif()
++  list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+   include(AddLLVM)
+   include(TableGen)
+   include(HandleLLVMOptions)
+@@ -99,7 +40,7 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
+     set(LLVM_INCLUDE_TESTS ON)
+   endif()
  
- set( LLVM_LINK_COMPONENTS
-   analysis
-@@ -63,10 +67,6 @@ option(LIBCLING_BUILD_STATIC
- #  set(LLVM_EXPORTED_SYMBOL_FILE)
- #endif()
+-  include_directories("${LLVM_BINARY_DIR}/include" "${LLVM_MAIN_INCLUDE_DIR}")
++  include_directories("${LLVM_INCLUDE_DIRS}")
+   link_directories("${LLVM_LIBRARY_DIR}")
  
--if( LLVM_ENABLE_PIC )
--  set(ENABLE_SHARED SHARED)
--endif()
--
- if((NOT LLVM_ENABLE_PIC OR LIBCLING_BUILD_STATIC) AND NOT WIN32)
-   set(ENABLE_STATIC STATIC)
- endif()
--- 
-2.33.0
-
+   set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin )