Support Xcode by not using CMake object libraries.

chrisdembia · chrisdembia · commit de8fd43cc172 · 2016-08-10T12:01:24.000-07:00
CMake allows specifying an object file as a source file for a library, but
Xcode does not allow creating a library whose source files are *only* object
files; there needs to be at least one real source file. This commit gets around
this issue by not using object library targets with Xcode.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -39,11 +39,20 @@ set(docopt_HEADERS
 #============================================================================
 # Compile targets
 #============================================================================
-add_library(docopt_o OBJECT ${docopt_SOURCES} ${docopt_HEADERS})
-set_target_properties(docopt_o PROPERTIES POSITION_INDEPENDENT_CODE TRUE)
-
-add_library(docopt SHARED $<TARGET_OBJECTS:docopt_o>)
-add_library(docopt_s STATIC $<TARGET_OBJECTS:docopt_o>)
+if(XCODE)
+    # Xcode does not support libraries with only object files as sources.
+    # See https://cmake.org/cmake/help/v3.0/command/add_library.html?highlight=add_library
+    add_library(docopt SHARED ${docopt_SOURCES} ${docopt_HEADERS})
+    add_library(docopt_s STATIC ${docopt_SOURCES} ${docopt_HEADERS})
+else()
+    # If not using Xcode, we will create an intermediate object target to avoid
+    # compiling the source code twice.
+    add_library(docopt_o OBJECT ${docopt_SOURCES} ${docopt_HEADERS})
+    set_target_properties(docopt_o PROPERTIES POSITION_INDEPENDENT_CODE TRUE)
+
+    add_library(docopt SHARED $<TARGET_OBJECTS:docopt_o>)
+    add_library(docopt_s STATIC $<TARGET_OBJECTS:docopt_o>)
+endif()
 
 target_include_directories(docopt PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}> $<INSTALL_INTERFACE:include/docopt>)
 target_include_directories(docopt_s PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}> $<INSTALL_INTERFACE:include/docopt>)
