From 3d315ba123ee3db9187411daa29839d3574714d8 Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Sat, 14 Mar 2020 14:19:13 -0300
Subject: [PATCH] More static build linking fixes

Static linking is a dumpster fire.
---
 CMakeLists.txt | 53 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 39 insertions(+), 14 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5058698..373d08b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,8 +37,14 @@ set(THREADS_PREFER_PTHREAD_FLAG ON)
 find_package(Threads REQUIRED)
 target_link_libraries(lokimq PRIVATE Threads::Threads)
 
-include(FindPkgConfig)
-pkg_search_module(libzmq QUIET libzmq>=4.3)
+# libzmq is nearly impossible to link statically from a system-installed static library: it depends
+# on a ton of other libraries which typically are not all statically available.  So if the caller
+# asked us to do things statically, don't even try to find a system lib and just build it.  If they
+# really want it, they can set up the libzmq_FOUND etc. variables themselves.
+if(BUILD_SHARED_LIBS)
+  include(FindPkgConfig)
+  pkg_search_module(libzmq QUIET libzmq>=4.3)
+endif()
 if(NOT libzmq_FOUND)
     message(STATUS "libzmq >= 4.3 not found, building bundled 4.3.2")
     list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/local-libzmq")
@@ -63,26 +69,45 @@ set_target_properties(lokimq PROPERTIES
     POSITION_INDEPENDENT_CODE ON
 )
 
-if(BUILD_SHARED_LIBS)
-  target_link_libraries(lokimq PUBLIC cppzmq)
-else()
-  target_link_libraries(lokimq PUBLIC cppzmq-static)
-endif()
-
 if(NOT SODIUM_LIBRARIES)
     pkg_search_module(SODIUM REQUIRED libsodium)
 endif()
 
+# allow adding links to non-local targets (which is allowed even under old policy as long as the
+# target is an interface, but under new cmake it spews out warnings).
+cmake_policy(SET CMP0079 NEW)
+
+function(link_dep_libs target linktype libdirs)
+  foreach(lib ${ARGN})
+    find_library(link_lib-${lib} NAMES ${lib} PATHS ${libdirs})
+    if(link_lib-${lib})
+      target_link_libraries(${target} ${linktype} ${link_lib-${lib}})
+    endif()
+  endforeach()
+endfunction()
+
 # Really want to just use SODIUM_LINK_LIBRARIES here, but that isn't in older cmake:
-find_library(libsodium_link_libs NAMES ${SODIUM_LIBRARIES} PATHS ${SODIUM_LIBRARY_DIRS})
-target_link_libraries(lokimq PRIVATE ${libsodium_link_libs})
+if(BUILD_SHARED_LIBS)
+  link_dep_libs(lokimq PRIVATE ${SODIUM_LIBRARY_DIRS} ${SODIUM_LIBRARIES})
+  target_include_directories(lokimq PRIVATE ${SODIUM_INCLUDE_DIRS})
 
-if(NOT BUILD_SHARED_LIBS)
-    target_link_libraries(cppzmq-static INTERFACE ${libsodium_link_libs})
+  target_link_libraries(lokimq PUBLIC cppzmq)
+else()
+  link_dep_libs(lokimq PRIVATE "${SODIUM_STATIC_LIBRARY_DIRS}" ${SODIUM_STATIC_LIBRARIES})
+  target_include_directories(lokimq PRIVATE ${SODIUM_STATIC_INCLUDE_DIRS})
+
+  if (libzmq_FOUND)
+    # cppzmq doesn't properly set up its libzmq target dependencies so do it here (this isn't the
+    # normal case: we only get here if someone pre-set libzmq_FOUND etc. *and* wants static libs)
+    link_dep_libs(cppzmq-static INTERFACE "${PC_LIBZMQ_STATIC_LIBRARY_DIRS}" ${PC_LIBZMQ_STATIC_LIBRARIES})
+  else()
+    # Otherwise we built a static vendored one, so make sure it links to the static libsodium
+    link_dep_libs(libzmq_vendor INTERFACE "${SODIUM_STATIC_LIBRARY_DIRS}" ${SODIUM_STATIC_LIBRARIES})
+  endif()
+
+  target_link_libraries(lokimq PUBLIC cppzmq-static)
 endif()
 
-target_include_directories(lokimq PRIVATE ${SODIUM_INCLUDE_DIRS})
-
 add_library(lokimq::lokimq ALIAS lokimq)
 
 export(