Problem: CMAKE_REQUIRED_INCLUDES used in a wrong way, check_function_exists is problematic

Solution: use check_cxx_symbol_exists resp. check_type_size instead

CMakeLists.txt

@@ -15,10 +15,9 @@ include(CheckCSourceCompiles)
 include(CheckCSourceRuns)
 include(CMakeDependentOption)
 include(CheckCXXSymbolExists)
-include(CheckSymbolExists)
+include(CheckTypeSize)
 include(FindThreads)
 include(GNUInstallDirs)
-include(CheckFunctionExists)
 include(CheckTypeSize)
 include(CMakePackageConfigHelpers)
 
@@ -154,21 +153,17 @@ set(POLLER "" CACHE STRING "Choose polling system for I/O threads. valid values
 
 if(NOT MSVC)
   if(POLLER STREQUAL "")
-    set(CMAKE_REQUIRED_INCLUDES sys/event.h)
-    check_function_exists(kqueue HAVE_KQUEUE)
-    set(CMAKE_REQUIRED_INCLUDES)
+    check_cxx_symbol_exists(kqueue sys/event.h HAVE_KQUEUE)
     if(HAVE_KQUEUE)
       set(POLLER "kqueue")
     endif()
   endif()
 
   if(POLLER STREQUAL "")
-    set(CMAKE_REQUIRED_INCLUDES sys/epoll.h)
-    check_function_exists(epoll_create HAVE_EPOLL)
-    set(CMAKE_REQUIRED_INCLUDES)
+    check_cxx_symbol_exists(epoll_create sys/epoll.h HAVE_EPOLL)
     if(HAVE_EPOLL)
       set(POLLER "epoll")
-      check_function_exists(epoll_create1 HAVE_EPOLL_CLOEXEC)
+      check_cxx_symbol_exists(epoll_create1 sys/epoll.h HAVE_EPOLL_CLOEXEC)
       if(HAVE_EPOLL_CLOEXEC)
         set(ZMQ_IOTHREAD_POLLER_USE_EPOLL_CLOEXEC 1)
       endif()
@@ -176,27 +171,23 @@ if(NOT MSVC)
   endif()
 
   if(POLLER STREQUAL "")
-    set(CMAKE_REQUIRED_INCLUDES sys/devpoll.h)
+    set(CMAKE_EXTRA_INCLUDE_FILES sys/devpoll.h)
     check_type_size("struct pollfd" DEVPOLL)
-    set(CMAKE_REQUIRED_INCLUDES)
+    set(CMAKE_EXTRA_INCLUDE_FILES)
     if(HAVE_DEVPOLL)
       set(POLLER "devpoll")
     endif()
   endif()
 
   if(POLLER STREQUAL "")
-    set(CMAKE_REQUIRED_INCLUDES sys/pollset.h)
-    check_function_exists(pollset_create HAVE_POLLSET)
-    set(CMAKE_REQUIRED_INCLUDES)
+    check_cxx_symbol_exists(pollset_create sys/pollset.h HAVE_POLLSET)
     if(HAVE_POLLSET)
       set(POLLER "pollset")
     endif()
   endif()
 
   if(POLLER STREQUAL "")
-    set(CMAKE_REQUIRED_INCLUDES poll.h)
-    check_function_exists(poll HAVE_POLL)
-    set(CMAKE_REQUIRED_INCLUDES)
+    check_cxx_symbol_exists(poll poll.h HAVE_POLL)
     if(HAVE_POLL)
       set(POLLER "poll")
     endif()
@@ -205,12 +196,9 @@ endif()
 
 if(POLLER STREQUAL "")
   if(WIN32)
-    set(CMAKE_REQUIRED_INCLUDES winsock2.h)
     set(HAVE_SELECT 1)
   else()
-    set(CMAKE_REQUIRED_INCLUDES sys/select.h)
-    check_function_exists(select HAVE_SELECT)
-    set(CMAKE_REQUIRED_INCLUDES)
+    check_cxx_symbol_exists(select sys/select.h HAVE_SELECT)
   endif()
   if(HAVE_SELECT)
     set(POLLER "select")
@@ -358,13 +346,13 @@ endif()
 if(ZMQ_HAVE_WINDOWS)
   # Cannot use check_library_exists because the symbol is always declared as char(*)(void)
   set(CMAKE_REQUIRED_LIBRARIES "ws2_32.lib")
-  check_symbol_exists(WSAStartup "winsock2.h" HAVE_WS2_32)
+  check_cxx_symbol_exists(WSAStartup "winsock2.h" HAVE_WS2_32)
 
   set(CMAKE_REQUIRED_LIBRARIES "rpcrt4.lib")
-  check_symbol_exists(UuidCreateSequential "rpc.h" HAVE_RPCRT4)
+  check_cxx_symbol_exists(UuidCreateSequential "rpc.h" HAVE_RPCRT4)
 
   set(CMAKE_REQUIRED_LIBRARIES "iphlpapi.lib")
-  check_symbol_exists(GetAdaptersAddresses "winsock2.h;iphlpapi.h" HAVE_IPHLAPI)
+  check_cxx_symbol_exists(GetAdaptersAddresses "winsock2.h;iphlpapi.h" HAVE_IPHLAPI)
 
   set(CMAKE_REQUIRED_LIBRARIES "")
   # TODO: This not the symbol we're looking for. What is the symbol?
@@ -397,28 +385,14 @@ endif()
 
 if(NOT MSVC)
   set(CMAKE_REQUIRED_LIBRARIES rt)
-  check_function_exists(clock_gettime HAVE_CLOCK_GETTIME)
+  check_cxx_symbol_exists(clock_gettime time.h HAVE_CLOCK_GETTIME)
   set(CMAKE_REQUIRED_LIBRARIES)
 
-  set(CMAKE_REQUIRED_INCLUDES unistd.h)
-  check_function_exists(fork HAVE_FORK)
-  set(CMAKE_REQUIRED_INCLUDES)
-
-  set(CMAKE_REQUIRED_INCLUDES sys/time.h)
-  check_function_exists(gethrtime HAVE_GETHRTIME)
-  set(CMAKE_REQUIRED_INCLUDES)
-
-  set(CMAKE_REQUIRED_INCLUDES stdlib.h)
-  check_function_exists(mkdtemp HAVE_MKDTEMP)
-  set(CMAKE_REQUIRED_INCLUDES)
-
-  set(CMAKE_REQUIRED_INCLUDES sys/socket.h)
-  check_function_exists(accept4 HAVE_ACCEPT4)
-  set(CMAKE_REQUIRED_INCLUDES)
-
-  set(CMAKE_REQUIRED_INCLUDES string.h)
-  check_function_exists(strnlen HAVE_STRNLEN)
-  set(CMAKE_REQUIRED_INCLUDES)
+  check_cxx_symbol_exists(fork unistd.h HAVE_FORK)
+  check_cxx_symbol_exists(gethrtimei sys/time.h HAVE_GETHRTIME)
+  check_cxx_symbol_exists(mkdtemp stdlib.h HAVE_MKDTEMP)
+  check_cxx_symbol_exists(accept4 sys/socket.h HAVE_ACCEPT4)
+  check_cxx_symbol_exists(strnlen string.h HAVE_STRNLEN)
 endif()
 
 add_definitions(-D_REENTRANT -D_THREAD_SAFE)