[libcxx-commits] [libcxx] 09943e8 - [libc++] Provide a default LLVM_PATH when building standalone

[Louis Dionne via libcxx-commits]

Author: Louis Dionne
Date: 2020-06-29T12:40:07-04:00
New Revision: 09943e8de1586dd7f28aa24879fd68717a859588

URL: https://github.com/llvm/llvm-project/commit/09943e8de1586dd7f28aa24879fd68717a859588
DIFF: https://github.com/llvm/llvm-project/commit/09943e8de1586dd7f28aa24879fd68717a859588.diff

LOG: [libc++] Provide a default LLVM_PATH when building standalone

Since we require that libc++ is built as part of the monorepo layout, we
can assume the path of the rest of LLVM and avoid requiring that LLVM_PATH
be set explicitly.

Added: 
    

Modified: 
    libcxx/cmake/Modules/HandleOutOfTreeLLVM.cmake
    libcxx/docs/BuildingLibcxx.rst

Removed: 
    


################################################################################
diff  --git a/libcxx/cmake/Modules/HandleOutOfTreeLLVM.cmake b/libcxx/cmake/Modules/HandleOutOfTreeLLVM.cmake
index 757450a6e475..d488b8ede7bf 100644
--- a/libcxx/cmake/Modules/HandleOutOfTreeLLVM.cmake
+++ b/libcxx/cmake/Modules/HandleOutOfTreeLLVM.cmake
@@ -1,3 +1,7 @@
+if (NOT DEFINED LLVM_PATH)
+  set(LLVM_PATH ${CMAKE_CURRENT_LIST_DIR}/../../../llvm CACHE PATH "" FORCE)
+endif()
+
 if(NOT IS_DIRECTORY ${LLVM_PATH})
   message(FATAL_ERROR
     "The provided LLVM_PATH (${LLVM_PATH}) is not a valid directory. Note that "

diff  --git a/libcxx/docs/BuildingLibcxx.rst b/libcxx/docs/BuildingLibcxx.rst
index 0fbb6693099c..c85c3d7fbcb6 100644
--- a/libcxx/docs/BuildingLibcxx.rst
+++ b/libcxx/docs/BuildingLibcxx.rst
@@ -52,21 +52,19 @@ The instructions are for building libc++ on
 FreeBSD, Linux, or Mac using `libc++abi`_ as the C++ ABI library.
 On Linux, it is also possible to use :ref:`libsupc++ <libsupcxx>` or libcxxrt.
 
-It is possible to keep your LLVM and libc++ trees separate so you can avoid
-rebuilding LLVM as often. An out-of-tree build would look like this:
+It is possible to build libc++ standalone (i.e. without building other LLVM
+projects). A standalone build would look like this:
 
 .. code-block:: bash
 
-  $ cd where-you-want-libcxx-to-live
-  $ # Check out the sources (includes everything, but we'll only use libcxx)
-  $ ``git clone https://github.com/llvm/llvm-project.git``
-  $ cd where-you-want-to-build
+  $ git clone https://github.com/llvm/llvm-project.git llvm-project
+  $ cd llvm-project
   $ mkdir build && cd build
-  $ export CC=clang CXX=clang++
-  $ cmake -DLLVM_PATH=path/to/separate/llvm \
+  $ cmake -DCMAKE_C_COMPILER=clang \
+          -DCMAKE_CXX_COMPILER=clang++ \
           -DLIBCXX_CXX_ABI=libcxxabi \
           -DLIBCXX_CXX_ABI_INCLUDE_PATHS=path/to/separate/libcxxabi/include \
-          path/to/llvm-project/libcxx
+          ../libcxx
   $ make
   $ make check-cxx # optional