Let the user choose the poller to use through cmake POLLER option

Use ccmake, or cmake -i, or cmake -DPOLLER=EPOLL, for example

CMakeLists.txt

@@ -24,6 +24,12 @@ include_directories(${ICONV_INCLUDE_DIR})
 # coming from these headers.
 include_directories(SYSTEM ${CRYPTO++_INCLUDE_DIR})
 
+set(POLLER "POLL" CACHE STRING
+  "Choose the poller between POLL and EPOLL (Linux-only)")
+if((NOT ${POLLER} MATCHES "POLL") AND
+    (NOT ${POLLER} MATCHES "EPOLL"))
+  message(FATAL_ERROR "POLLER must be either POLL or EPOLL")
+endif()
 #
 ## utils
 #
@@ -95,4 +101,4 @@ target_link_libraries(test
   utils
   config)
 
-CONFIGURE_FILE(config.h.cmake src/config.h @ONLY)
+configure_file(config.h.cmake src/config.h)

config.h.cmake

 #cmakedefine ICONV_SECOND_ARGUMENT_IS_CONST
+#cmakedefine POLLER ${POLLER}

src/network/poller.hpp

@@ -9,11 +9,9 @@
 #define POLL 1
 #define EPOLL 2
 #define KQUEUE 3
-
 #include <config.h>
 #ifndef POLLER
-  // Default standard poller
-  #define POLLER EPOLL
+ #define POLLER POLL
 #endif
 
 #if POLLER == POLL
@@ -21,6 +19,8 @@
  #define MAX_POLL_FD_NUMBER 4096
 #elif POLLER == EPOLL
   #include <sys/epoll.h>
+#else
+  #error Invalid POLLER value
 #endif
 
 /**