Add support for shared library build

Author: makkarpov

.gitignore

@@ -7,4 +7,8 @@ bazel-spirv-reflect
 bazel-SPIRV-Reflect
 bazel-testlogs
 /.vs
-/.vscode
+/.vscode
+
+# CLion-specific:
+/.idea
+/cmake-build*

CMakeLists.txt

@@ -2,6 +2,7 @@ cmake_minimum_required(VERSION 3.5)
 
 project(spirv-reflect)
 
+OPTION(BUILD_SHARED_LIBS            "Build shared library" OFF)
 OPTION(SPIRV_REFLECT_EXECUTABLE     "Build spirv-reflect executable" ON)
 
 OPTION(SPIRV_REFLECT_STATIC_LIB     "Build a SPIRV-Reflect static library" OFF)
@@ -12,14 +13,15 @@ OPTION(SPIRV_REFLECT_ENABLE_ASAN    "Use address sanitization" OFF)
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 set(CMAKE_CXX_STANDARD 14)
 
-set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin")
 
 if (SPIRV_REFLECT_ENABLE_ASAN)
     add_compile_options(-fsanitize=address -fno-omit-frame-pointer)
     add_link_options(-fsanitize=address)
 endif()
 
 if (SPIRV_REFLECT_EXECUTABLE)
+    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin")
+
     # ==========================================================================
     # Compile spirv_reflect.c as C
     # ==========================================================================
@@ -118,3 +120,18 @@ if(SPIRV_REFLECT_STATIC_LIB)
             ARCHIVE DESTINATION lib)
 endif()
 
+if(BUILD_SHARED_LIBS)
+    add_library(spirv-reflect SHARED ${CMAKE_CURRENT_SOURCE_DIR}/spirv_reflect.h
+            ${CMAKE_CURRENT_SOURCE_DIR}/spirv_reflect.c)
+
+    target_include_directories(spirv-reflect
+            PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+
+    target_compile_definitions(spirv-reflect PUBLIC SPIRV_REFLECT_SHARED)
+    target_compile_options(spirv-reflect PRIVATE
+            $<$<CXX_COMPILER_ID:GNU>:-fvisibility=hidden>)
+
+    install(TARGETS spirv-reflect
+            LIBRARY DESTINATION lib
+            ARCHIVE DESTINATION lib)
+endif ()

README.md

@@ -49,6 +49,26 @@ If the project wants to use it's own SPIRV-Header path, it can set `SPIRV_REFLEC
 target_compile_definitions(project_name PUBLIC SPIRV_REFLECT_USE_SYSTEM_SPIRV_H)
 ```
 
+### Building a shared library
+
+To facilitate integration into managed languages with FFI support (such as Java and Python), 
+this project could be built as a shared library. This mode is controlled by the `BUILD_SHARED_LIBS`
+CMake option:
+
+```shell
+mkdir build && cd build
+cmake -DBUILD_SHARED_LIBS=ON -DSPIRV_REFLECT_EXECUTABLE=OFF ..
+make
+``` 
+
+Please note that shared library mode is not intended for anything else but this. **Especially** it 
+is not intended for the regular use case of the shared libraries: packaging and shipping a single 
+global library for all applications in the system. Header files of SPIRV-Reflect expose several C 
+structures that you are supposed to allocate by yourself without any way of communicating the 
+actual runtime structure size. Therefore, you must treat the resulting artifact in the same way 
+you are dealing with static libraries: runtime library version must **exactly** match the version 
+of `spirv_reflect.h` file you used to  compile your app or generate its FFI bindings.
+
 ## Building Samples
 
 **This step is only necessary when building/running SPIRV-Reflect's example applications.**

spirv_reflect.c

@@ -14,6 +14,7 @@
  limitations under the License.
 */
 
+#define SPIRV_REFLECT_IMPLEMENTATION  // turn dllimports into dllexports
 #include "spirv_reflect.h"
 
 #include <assert.h>