From 2e98b68e3bbcba08de428f7a0c20427d547803cf Mon Sep 17 00:00:00 2001
From: Sam Edwards <CFSworks@gmail.com>
Date: Sun, 10 Jun 2018 01:46:36 -0600
Subject: [PATCH] CMake: Make directbase/pandabase INTERFACE libraries

They export no code, and are really only used to contain several
preprocessor macros relevant to their respective packages. On
Windows, they're a problem: MSVC doesn't generate a .lib when
compiling a .dll that exports nothing.
---
 cmake/macros/BuildMetalib.cmake      | 19 ++++++++++++-------
 direct/CMakeLists.txt                |  2 +-
 direct/src/directbase/CMakeLists.txt |  8 +++-----
 panda/src/pandabase/CMakeLists.txt   |  6 +++---
 4 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/cmake/macros/BuildMetalib.cmake b/cmake/macros/BuildMetalib.cmake
index 7b804bd1b9..716f8c09d8 100644
--- a/cmake/macros/BuildMetalib.cmake
+++ b/cmake/macros/BuildMetalib.cmake
@@ -30,24 +30,29 @@ function(target_link_libraries target)
       set_property(TARGET "${target}" APPEND PROPERTY INCLUDE_DIRECTORIES "${include_directories}")
       set_property(TARGET "${target}" APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${include_directories}")
 
-      # Also build with the same BUILDING_ macros, because these will all end
-      # up in the same library.
-      set(compile_definitions "$<$<BOOL:$<TARGET_PROPERTY:${library},IS_COMPONENT>>:$<TARGET_PROPERTY:${library},COMPILE_DEFINITIONS>>")
-      set_property(TARGET "${target}" APPEND PROPERTY COMPILE_DEFINITIONS "${compile_definitions}")
-
       # Libraries are only linked transitively if they aren't components.
       # Unfortunately, it seems like INTERFACE_LINK_LIBRARIES can't have
       # generator expressions on an object library(?) so we resort to taking
       # care of this at configuration time.
       if(TARGET "${library}")
-        get_target_property(is_component "${library}" IS_COMPONENT)
+        get_target_property(target_type "${library}" TYPE)
+        if(NOT target_type STREQUAL "INTERFACE_LIBRARY")
+          get_target_property(is_component "${library}" IS_COMPONENT)
+        else()
+          set(is_component OFF)
+        endif()
       else()
         # This is a safe assumption, since we define all component libraries
         # before the metalib they appear in:
         set(is_component OFF)
       endif()
 
-      if(NOT is_component)
+      if(is_component)
+        # Also build with the same BUILDING_ macros, because these will all end
+        # up in the same library.
+        set(compile_definitions "$<TARGET_PROPERTY:${library},COMPILE_DEFINITIONS>")
+        set_property(TARGET "${target}" APPEND PROPERTY COMPILE_DEFINITIONS "${compile_definitions}")
+      else()
         set_property(TARGET "${target}" APPEND PROPERTY INTERFACE_LINK_LIBRARIES "${library}")
       endif()
     else()
diff --git a/direct/CMakeLists.txt b/direct/CMakeLists.txt
index 14ea20eca3..9e6e238d03 100644
--- a/direct/CMakeLists.txt
+++ b/direct/CMakeLists.txt
@@ -15,7 +15,7 @@ add_subdirectory(src/motiontrail)
 add_subdirectory(src/showbase)
 
 set(P3DIRECT_COMPONENTS
-  p3dcparser p3deadrec p3directbase
+  p3dcparser p3deadrec
   p3interval p3motiontrail p3showbase)
 if(HAVE_PYTHON)
   list(APPEND P3DIRECT_COMPONENTS p3distributed)
diff --git a/direct/src/directbase/CMakeLists.txt b/direct/src/directbase/CMakeLists.txt
index 447c93f12d..53a8de1ee7 100644
--- a/direct/src/directbase/CMakeLists.txt
+++ b/direct/src/directbase/CMakeLists.txt
@@ -6,10 +6,8 @@ set(P3DIRECTBASE_HEADERS
   directbase.h directsymbols.h
 )
 
-# Not worth compositing sources, there's really only one.
-add_component_library(p3directbase NOINIT
-  ${P3DIRECTBASE_HEADERS} ${P3DIRECTBASE_SOURCES})
-target_link_libraries(p3directbase panda)
+# Yes, INTERFACE: don't build it, there's no code!
+add_library(p3directbase INTERFACE)
+target_link_libraries(p3directbase INTERFACE panda)
 
-install(TARGETS p3directbase DESTINATION lib)
 install(FILES ${P3DIRECTBASE_HEADERS} DESTINATION include/panda3d)
diff --git a/panda/src/pandabase/CMakeLists.txt b/panda/src/pandabase/CMakeLists.txt
index 4e9b89735c..3cf44a1228 100644
--- a/panda/src/pandabase/CMakeLists.txt
+++ b/panda/src/pandabase/CMakeLists.txt
@@ -6,8 +6,8 @@ set(P3PANDABASE_SOURCES
   pandabase.cxx
 )
 
-add_component_library(p3pandabase ${P3PANDABASE_HEADERS} ${P3PANDABASE_SOURCES})
-target_link_libraries(p3pandabase p3dtool)
+# Yes, INTERFACE: don't build it, there's no code!
+add_library(p3pandabase INTERFACE)
+target_link_libraries(p3pandabase INTERFACE p3dtool)
 
-install(TARGETS p3pandabase DESTINATION lib)
 install(FILES ${P3PANDABASE_HEADERS} DESTINATION include/panda3d)