[Lldb-commits] [PATCH] D65798: [lldb][CMake] Infer `Clang_DIR` if not passed explicitly

[Stefan Gränitz via Phabricator via lldb-commits]

sgraenitz updated this revision to Diff 213842.
sgraenitz added a comment.

Update documentation to mention multiple provided build trees and the usage of `Clang_DIR`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65798/new/

https://reviews.llvm.org/D65798

Files:
  lldb/cmake/modules/LLDBStandalone.cmake
  lldb/docs/resources/build.rst


Index: lldb/docs/resources/build.rst
===================================================================
--- lldb/docs/resources/build.rst
+++ lldb/docs/resources/build.rst
@@ -120,10 +120,11 @@
 *****************
 
 This is another way to build LLDB. We can use the same source-tree as we
-checked out above, but now we will have two build-trees:
+checked out above, but now we will have multiple build-trees:
 
 * the main build-tree for LLDB in ``/path/to/lldb-build``
-* a provided build-tree for LLVM and Clang in ``/path/to/llvm-build``
+* one or more provided build-trees for LLVM and Clang; for simplicity we use a
+  single one in ``/path/to/llvm-build``
 
 Run CMake with ``-B`` pointing to a new directory for the provided
 build-tree\ :sup:`1` and the positional argument pointing to the ``llvm``
@@ -139,15 +140,15 @@
 
 Now run CMake a second time with ``-B`` pointing to a new directory for the
 main build-tree and the positional argument pointing to the ``lldb`` directory
-in the source-tree. In order to find the provided build-tree, the build-system
-needs the options ``LLVM_DIR`` and ``Clang_DIR`` (CMake variables are
-case-sensitive!):
+in the source-tree. In order to find the provided build-tree, the build system
+looks for the path to its CMake modules in ``LLVM_DIR``. If you use a separate
+build directory for Clang, remember to pass its module path via ``Clang_DIR``
+(CMake variables are case-sensitive!):
 
 ::
 
   > cmake -B /path/to/lldb-build -G Ninja \
           -DLLVM_DIR=/path/to/llvm-build/lib/cmake/llvm \
-          -DClang_DIR=/path/to/llvm-build/lib/cmake/clang \
           [<more cmake options>] /path/to/llvm-project/lldb
   > ninja lldb
 
@@ -323,7 +324,6 @@
   > cmake -B /path/to/lldb-build \
           -C /path/to/llvm-project/lldb/cmake/caches/Apple-lldb-Xcode.cmake \
           -DLLVM_DIR=/path/to/llvm-build/lib/cmake/llvm \
-          -DClang_DIR=/path/to/llvm-build/lib/cmake/clang \
           llvm-project/lldb
   > open lldb.xcodeproj
   > cmake --build /path/to/lldb-build --target check-lldb
Index: lldb/cmake/modules/LLDBStandalone.cmake
===================================================================
--- lldb/cmake/modules/LLDBStandalone.cmake
+++ lldb/cmake/modules/LLDBStandalone.cmake
@@ -1,5 +1,11 @@
 option(LLVM_INSTALL_TOOLCHAIN_ONLY "Only include toolchain files in the 'install' target." OFF)
 
+# If Clang was built in one tree with LLVM, we can infer its CMake module directory.
+if(NOT Clang_DIR AND EXISTS ${LLVM_DIR}/../clang)
+  set(Clang_DIR ${LLVM_DIR}/../clang)
+  message(STATUS "Inferred Clang_DIR: ${Clang_DIR}")
+endif()
+
 find_package(LLVM REQUIRED CONFIG HINTS "${LLVM_DIR}" NO_CMAKE_FIND_ROOT_PATH)
 find_package(Clang REQUIRED CONFIG HINTS "${Clang_DIR}" NO_CMAKE_FIND_ROOT_PATH)
 


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