cmake: Add libzmq optional package support

CMakeLists.txt

@@ -49,6 +49,7 @@ include(TristateOption)
 tristate_option(CCACHE "Use ccache for compiling." "if ccache is found." AUTO)
 tristate_option(WITH_NATPMP "Enable NAT-PMP." "if libnatpmp is found." AUTO)
 tristate_option(WITH_MINIUPNPC "Enable UPnP." "if libminiupnpc is found." AUTO)
+tristate_option(WITH_ZMQ "Enable ZMQ notifications." "if libzmq is found." AUTO)
 
 if(CXX20)
   set(CMAKE_CXX_STANDARD 20)
@@ -145,6 +146,7 @@ message("  bitcoind ............................ ${BUILD_DAEMON}")
 message("Optional packages:")
 message("  NAT-PMP ............................. ${WITH_NATPMP}")
 message("  UPnP ................................ ${WITH_MINIUPNPC}")
+message("  ZeroMQ .............................. ${WITH_ZMQ}")
 message("")
 if(CMAKE_CROSSCOMPILING)
   set(cross_status "TRUE, for ${CMAKE_SYSTEM_NAME}, ${CMAKE_SYSTEM_PROCESSOR}")

cmake/optional.cmake

@@ -57,3 +57,31 @@ if(WITH_MINIUPNPC)
     message(FATAL_ERROR "libminiupnpc requested, but not found.")
   endif()
 endif()
+
+if(WITH_ZMQ)
+  if(MSVC)
+    find_package(ZeroMQ CONFIG)
+  else()
+    # The ZeroMQ project has provided config files since v4.2.2.
+    # TODO: Switch to find_package(ZeroMQ) at some point in the future.
+    include(CrossPkgConfig)
+    cross_pkg_check_modules(libzmq IMPORTED_TARGET libzmq>=4)
+    if(libzmq_FOUND)
+      set_property(TARGET PkgConfig::libzmq APPEND PROPERTY
+        INTERFACE_COMPILE_DEFINITIONS $<$<PLATFORM_ID:Windows>:ZMQ_STATIC>
+      )
+      set_property(TARGET PkgConfig::libzmq APPEND PROPERTY
+        INTERFACE_LINK_LIBRARIES $<$<PLATFORM_ID:Windows>:iphlpapi;ws2_32>
+      )
+    endif()
+  endif()
+  if(TARGET libzmq OR TARGET PkgConfig::libzmq)
+    set(WITH_ZMQ ON)
+  elseif(WITH_ZMQ STREQUAL "AUTO")
+    message(WARNING "libzmq not found, disabling.\n"
+                    "To skip libzmq check, use \"-DWITH_ZMQ=OFF\".\n")
+    set(WITH_ZMQ OFF)
+  else()
+    message(FATAL_ERROR "libzmq requested, but not found.")
+  endif()
+endif()

src/CMakeLists.txt

@@ -29,6 +29,9 @@ add_library(bitcoin_consensus OBJECT EXCLUDE_FROM_ALL
 )
 target_link_libraries(bitcoin_consensus PRIVATE secp256k1)
 
+if(WITH_ZMQ)
+  add_subdirectory(zmq EXCLUDE_FROM_ALL)
+endif()
 
 # Home for common functionality shared by different executables and libraries.
 # Similar to `bitcoin_util` library, but higher-level.
@@ -188,6 +191,7 @@ target_link_libraries(bitcoin_node
     $<TARGET_NAME_IF_EXISTS:PkgConfig::libevent_pthreads>
     $<TARGET_NAME_IF_EXISTS:NATPMP::NATPMP>
     $<TARGET_NAME_IF_EXISTS:MiniUPnPc::MiniUPnPc>
+    $<TARGET_NAME_IF_EXISTS:bitcoin_zmq>
 )
 
 

src/zmq/CMakeLists.txt

@@ -0,0 +1,22 @@
+# Copyright (c) 2023 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+add_library(bitcoin_zmq STATIC
+  zmqabstractnotifier.cpp
+  zmqnotificationinterface.cpp
+  zmqpublishnotifier.cpp
+  zmqrpc.cpp
+  zmqutil.cpp
+)
+target_compile_definitions(bitcoin_zmq
+  INTERFACE
+    ENABLE_ZMQ=1
+)
+target_link_libraries(bitcoin_zmq
+  PRIVATE
+    leveldb
+    univalue
+    $<TARGET_NAME_IF_EXISTS:libzmq>
+    $<TARGET_NAME_IF_EXISTS:PkgConfig::libzmq>
+)