CMake: pkg-config Fallback

Try to find installs of `libzmq` that were performed with
autotools with a `pkg-config` fallback.

Author: ax3l

CMakeLists.txt

@@ -1,7 +1,35 @@
 cmake_minimum_required(VERSION 2.8.12)
 project(cppzmq)
 
-find_package(ZeroMQ REQUIRED)
+find_package(ZeroMQ)
+
+# libzmq autotools install: fallback to pkg-config
+if(NOT ZeroMQ_FOUND)
+    find_package(PkgConfig)
+    pkg_check_modules(PC_LIBZMQ QUIET libzmq)
+
+    set(ZeroMQ_VERSION ${PC_LIBZMQ_VERSION})
+    find_library(ZeroMQ_LIBRARY NAMES libzmq.so
+                 PATHS ${PC_LIBZMQ_LIBDIR} ${PC_LIBZMQ_LIBRARY_DIRS})
+    find_library(ZeroMQ_STATIC_LIBRARY NAMES libzmq.a
+                 PATHS ${PC_LIBZMQ_LIBDIR} ${PC_LIBZMQ_LIBRARY_DIRS})
+
+    add_library(libzmq SHARED IMPORTED)
+    set_property(TARGET libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq PROPERTY IMPORTED_LOCATION ${ZeroMQ_LIBRARY})
+
+    add_library(libzmq-static STATIC IMPORTED ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq-static PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq-static PROPERTY IMPORTED_LOCATION ${ZeroMQ_STATIC_LIBRARY})
+
+    if(ZeroMQ_LIBRARY AND ZeroMQ_STATIC_LIBRARY)
+        set(ZeroMQ_FOUND ON)
+    endif()
+endif()
+
+if(NOT ZeroMQ_FOUND)
+    message(FATAL_ERROR "ZeroMQ was NOT found!")
+endif()
 
 if (ZeroMQ_FOUND AND (NOT TARGET libzmq OR NOT TARGET libzmq-static))
   message(FATAL_ERROR "ZeroMQ version not supported!")

cppzmqConfig.cmake.in

@@ -17,7 +17,35 @@
 @PACKAGE_INIT@
 
 include(CMakeFindDependencyMacro)
-find_dependency(ZeroMQ)
+find_package(ZeroMQ)
+
+# libzmq autotools install: fallback to pkg-config
+if(NOT ZeroMQ_FOUND)
+    find_package(PkgConfig)
+    pkg_check_modules(PC_LIBZMQ QUIET libzmq)
+
+    set(ZeroMQ_VERSION ${PC_LIBZMQ_VERSION})
+    find_library(ZeroMQ_LIBRARY NAMES libzmq.so
+                 PATHS ${PC_LIBZMQ_LIBDIR} ${PC_LIBZMQ_LIBRARY_DIRS})
+    find_library(ZeroMQ_STATIC_LIBRARY NAMES libzmq.a
+                 PATHS ${PC_LIBZMQ_LIBDIR} ${PC_LIBZMQ_LIBRARY_DIRS})
+
+    add_library(libzmq SHARED IMPORTED)
+    set_property(TARGET libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq PROPERTY IMPORTED_LOCATION ${ZeroMQ_LIBRARY})
+
+    add_library(libzmq-static STATIC IMPORTED ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq-static PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PC_LIBZMQ_INCLUDE_DIRS})
+    set_property(TARGET libzmq-static PROPERTY IMPORTED_LOCATION ${ZeroMQ_STATIC_LIBRARY})
+
+    if(ZeroMQ_LIBRARY AND ZeroMQ_STATIC_LIBRARY)
+        set(ZeroMQ_FOUND ON)
+    endif()
+endif()
+
+if(NOT ZeroMQ_FOUND)
+    message(FATAL_ERROR "ZeroMQ was NOT found!")
+endif()
 
 if(NOT TARGET @PROJECT_NAME@)
   include("${CMAKE_CURRENT_LIST_DIR}/@[email protected]")