Fix #82: Make static linking optional

The executable is still linked against `.a` Clang libraries.

Author: jonas

README.md

@@ -66,6 +66,12 @@ make
 ./scala-native-bindgen /usr/include/ctype.h -name ctype --
 ```
 
+To build a statically linked executable pass `-DSTATIC_LINKING=ON` when invoking `cmake`:
+
+```sh
+cmake -DSTATIC_LINKING=ON ..
+```
+
 Alternatively, you can use [docker-compose] to build and test the program:
 
 ```sh

bindgen/CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.9)
 project(scala-native-bindgen)
 
-set(USE_SHARED OFF)
+option(STATIC_LINKING "Statically link the executable" OFF)
 
 # Locate LLVMConfig.cmake
 find_package(LLVM REQUIRED CONFIG)
@@ -14,22 +14,11 @@ include_directories(SYSTEM ${LLVM_INCLUDE_DIRS})
 message(STATUS "Using LLVM defs: ${LLVM_DEFINITIONS}")
 add_definitions(${LLVM_DEFINITIONS})
 
-add_compile_options(-fexceptions -std=c++11 -Wall -Wconversion -Werror)
-
-if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-  # macOS does not guarantee backwards compatible system calls and therefore
-  # discourages statically linked binaries. Instead add -L/usr/lib before the
-  # LLVM LDFLAGS to link against the dynamic system libc++ instead of the one
-  # from LLVM.
-  set(BINDGEN_LINK_FLAG "-L/usr/lib")
-else()
-  set(BINDGEN_LINK_FLAG "-static")
-endif()
-message(STATUS "Using link flag: ${BINDGEN_LINK_FLAG}")
-
 message(STATUS "Using LLVM library directories: ${LLVM_LIBRARY_DIRS}")
 link_directories(${LLVM_LIBRARY_DIRS})
 
+add_compile_options(-fexceptions -std=c++11 -Wall -Wconversion -Werror)
+
 add_executable(bindgen
   Main.cpp
   visitor/ScalaFrontendAction.h
@@ -85,14 +74,29 @@ add_executable(bindgen
   ir/types/ArrayType.h
 )
 
+if (STATIC_LINKING)
+  set(USE_SHARED OFF)
+  if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+    # macOS does not guarantee backwards compatible system calls and therefore
+    # discourages statically linked binaries. Instead add -L/usr/lib before the
+    # LLVM LDFLAGS to link against the dynamic system libc++ instead of the one
+    # from LLVM.
+    set(BINDGEN_LINK_FLAG "-L/usr/lib")
+  else()
+    set(BINDGEN_LINK_FLAG "-static")
+  endif()
+  llvm_map_components_to_libnames(LLVM_LIBS support core irreader object option profiledata)
+else()
+  set(LLVM_LIBS LLVM)
+endif()
+message(STATUS "Using link flag: ${BINDGEN_LINK_FLAG}")
+
 set_target_properties(bindgen
   PROPERTIES
   OUTPUT_NAME scala-native-bindgen
   LINK_FLAGS "${BINDGEN_LINK_FLAG}"
 )
 
-llvm_map_components_to_libnames(LLVM_LIBS support core irreader object option profiledata)
-
 target_link_libraries(bindgen
   PRIVATE
   clangFrontend

bindgen/Dockerfile

@@ -8,7 +8,7 @@ COPY . /src
 RUN set -x \
  && mkdir target \
  && cd target \
- && cmake .. \
+ && cmake -DSTATIC_LINKING=ON .. \
  && make
 
 FROM scratch