cmake: disable poll for macOS

Mirrors the autotools behavior introduced with curl-7_50_3-83-ga34c7ce.

Fixes curl#1089

Author: Lekensteyn

CMake/OtherTests.cmake

@@ -179,17 +179,20 @@ int main(void) {
 
 
 include(CheckCSourceRuns)
-set(CMAKE_REQUIRED_FLAGS)
-if(HAVE_SYS_POLL_H)
-  set(CMAKE_REQUIRED_FLAGS "-DHAVE_SYS_POLL_H")
-endif(HAVE_SYS_POLL_H)
-check_c_source_runs("
-  #ifdef HAVE_SYS_POLL_H
-  #  include <sys/poll.h>
-  #endif
-  int main(void) {
-    return poll((void *)0, 0, 10 /*ms*/);
-  }" HAVE_POLL_FINE)
+# See HAVE_POLL in CMakeLists.txt for why poll is disabled on macOS
+if(NOT APPLE)
+  set(CMAKE_REQUIRED_FLAGS)
+  if(HAVE_SYS_POLL_H)
+    set(CMAKE_REQUIRED_FLAGS "-DHAVE_SYS_POLL_H")
+  endif(HAVE_SYS_POLL_H)
+  check_c_source_runs("
+    #ifdef HAVE_SYS_POLL_H
+    #  include <sys/poll.h>
+    #endif
+    int main(void) {
+      return poll((void *)0, 0, 10 /*ms*/);
+    }" HAVE_POLL_FINE)
+endif()
 
 set(HAVE_SIG_ATOMIC_T 1)
 set(CMAKE_REQUIRED_FLAGS)

CMakeLists.txt

@@ -742,7 +742,11 @@ endif()
 
 check_symbol_exists(basename      "${CURL_INCLUDES}" HAVE_BASENAME)
 check_symbol_exists(socket        "${CURL_INCLUDES}" HAVE_SOCKET)
-check_symbol_exists(poll          "${CURL_INCLUDES}" HAVE_POLL)
+# poll on macOS is unreliable, it first did not exist, then was broken until
+# fixed in 10.9 only to break again in 10.12.
+if(NOT APPLE)
+  check_symbol_exists(poll        "${CURL_INCLUDES}" HAVE_POLL)
+endif()
 check_symbol_exists(select        "${CURL_INCLUDES}" HAVE_SELECT)
 check_symbol_exists(strdup        "${CURL_INCLUDES}" HAVE_STRDUP)
 check_symbol_exists(strstr        "${CURL_INCLUDES}" HAVE_STRSTR)