build: Separate shared and static library targets (#1293)

This splits the target so that we always build static libraries, but
optionally also build shared libraries. This also tweaks the
installation so that the static library is never installed, because it
is not usable without the other internal static library deps. The
headers and pkgconfig will only be installed if we have a shared library
to use them with.

packager/CMakeLists.txt

@@ -88,14 +88,7 @@ set(libpackager_sources
   ../include/packager/packager.h
 )
 
-if(BUILD_SHARED_LIBS)
+set(libpackager_deps
-  add_library(libpackager SHARED ${libpackager_sources})
-  target_compile_definitions(libpackager PUBLIC SHAKA_IMPLEMENTATION)
-else()
-  add_library(libpackager STATIC ${libpackager_sources})
-endif()
-
-target_link_libraries(libpackager
   file
   hls_builder
   media_chunking
@@ -117,9 +110,38 @@ target_link_libraries(libpackager
   string_utils
   version
 )
-# Avoid liblibpackager on Windows:
+
+# A static library target is always built.
+add_library(libpackager_static STATIC ${libpackager_sources})
+target_link_libraries(libpackager_static ${libpackager_deps})
+
+# And always installed as libpackager.a:
 if(NOT MSVC)
-  set_property(TARGET libpackager PROPERTY OUTPUT_NAME packager)
+  set_property(TARGET libpackager_static PROPERTY OUTPUT_NAME packager)
+else()
+  set_property(TARGET libpackager_static PROPERTY OUTPUT_NAME libpackager)
+endif()
+
+# A shared library target is conditional (default OFF):
+if(BUILD_SHARED_LIBS)
+  add_library(libpackager_shared SHARED ${libpackager_sources})
+  target_link_libraries(libpackager_shared ${libpackager_deps})
+  target_compile_definitions(libpackager_shared PUBLIC SHAKA_IMPLEMENTATION)
+
+  # And always installed as libpackager.so / libpackager.dll:
+  if(NOT MSVC)
+    set_property(TARGET libpackager_shared PROPERTY OUTPUT_NAME packager)
+  else()
+    set_property(TARGET libpackager_shared PROPERTY OUTPUT_NAME libpackager)
+  endif()
+
+  # If we're building a shared library, this is what the "libpackager" target
+  # aliases to.
+  add_library(libpackager ALIAS libpackager_shared)
+else()
+  # If we're not building a shared library, the "libpackager" target aliases to
+  # the static library.
+  add_library(libpackager ALIAS libpackager_static)
 endif()
 
 add_executable(packager
@@ -223,15 +245,22 @@ endif()
 
 configure_file(packager.pc.in packager.pc @ONLY)
 
-install(DIRECTORY ../include/packager
+# Always install the binaries.
-  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+install(TARGETS mpd_generator packager)
-
-install(TARGETS mpd_generator packager libpackager)
 
+# Always install the python tools.
 install(PROGRAMS ${CMAKE_BINARY_DIR}/pssh-box.py
   DESTINATION ${CMAKE_INSTALL_BINDIR})
 install(DIRECTORY ${CMAKE_BINARY_DIR}/pssh-box-protos
   DESTINATION ${CMAKE_INSTALL_BINDIR})
 
+# With shared libraries, also install the library, headers, and pkgconfig.
+# The static library isn't usable as a standalone because it doesn't include
+# its static dependencies (zlib, absl, etc).
+if(BUILD_SHARED_LIBS)
+  install(TARGETS libpackager_shared)
+  install(DIRECTORY ../include/packager
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
   install(FILES ${CMAKE_BINARY_DIR}/packager/packager.pc
     DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
+endif()