linux-packaging-mono/external/corert/Documentation/how-to-build-ObjectWriter.md

Build ObjectWriter library

ObjWriter is based on LLVM, so it requires recent CMake and GCC/Clang to build LLVM. See LLVM requirements for more details.

build.cmd/build.sh script downloads a pre-built ObjWriter NuGet package. ObjWriter library is not built by default because it takes a long time and changes rarely.

To build a fresh ObjWriter, pass additional objwriter argument to the build.cmd/build.sh script. It will cause the build to clone a matching copy of LLVM and use it to build ObjWriter library.

The following manual steps are useful for troubleshooting ObjWriter build issues.

1. Clone LLVM from official LLVM mirror github git repository:

   git clone -b release_50 https://github.com/llvm-mirror/llvm.git
   

2. Copy ObjWriter directory from CoreRT into LLVM tree

   cp -r corert/src/Native/ObjWriter llvm/tools/
   

3. Apply the patch to LLVM:

   cd llvm
   git apply tools/ObjWriter/llvm.patch
   

4. Configure and build LLVM with ObjWriter:

   mkdir build
   cd build
   cmake ../ -DCMAKE_BUILD_TYPE=Release -DLLVM_OPTIMIZED_TABLEGEN=1 -DHAVE_POSIX_SPAWN=0 -DLLVM_ENABLE_PIC=1 -DLLVM_BUILD_TESTS=0 -DLLVM_ENABLE_DOXYGEN=0 -DLLVM_INCLUDE_DOCS=0 -DLLVM_INCLUDE_TESTS=0
   make -j10 objwriter
   cd ..
   

• For ARM(cross/non-cross) please specify Triple for LLVM as Cmake configuration option:

  -DLLVM_DEFAULT_TARGET_TRIPLE=thumbv7-linux-gnueabi
  

• You can change the building type(CMAKE_BUILD_TYPE) to the debugging type(Debug), if necessary to debug ObjWriter.
• Also, you can do this under chroot to building ObjWriter for other platforms.

5. Get ObjWriter:

   If all goes well, the build will complete in the previous step and you will get ObjWriter library as llvm/build/lib/libobjwriter.so