CMake: remove test for eventfd, replace with __has_include

This also removes the configure option and therefore makes the feature
not disable-able. Saves 350 ms of CMake time.

Change-Id: Ifbf974a4d10745b099b1fffd17775528767595d4
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

cmake/configure-cmake-mapping.md

@@ -113,7 +113,6 @@ The following table describes the mapping of configure options to CMake argument
 | -doubleconversion                     | -DFEATURE_doubleconversion=ON                     |                                                                 |
 |                                       | -DFEATURE_system_doubleconversion=ON/OFF          |                                                                 |
 | -glib                                 | -DFEATURE_glib=ON                                 |                                                                 |
-| -eventfd                              | -DFEATURE_eventfd=ON                              |                                                                 |
 | -inotify                              | -DFEATURE_inotify=ON                              |                                                                 |
 | -icu                                  | -DFEATURE_icu=ON                                  |                                                                 |
 | -pcre                                 | -DFEATURE_pcre2=ON                                |                                                                 |

config_help.txt

@@ -221,7 +221,6 @@ Core options:
   -doubleconversion .... Select used double conversion library [system/qt/no]
                          No implies use of sscanf_l and snprintf_l (imprecise).
   -glib ................ Enable Glib support [no; auto on Unix]
-  -eventfd ............. Enable eventfd support
   -inotify ............. Enable inotify support
   -icu ................. Enable ICU support [auto]
   -pcre ................ Select used libpcre2 [system/qt/no]

src/corelib/configure.cmake

@@ -172,24 +172,6 @@ int main(void)
 }"
 )
 
-# eventfd
-qt_config_compile_test(eventfd
-    LABEL "eventfd"
-    CODE
-"#include <sys/eventfd.h>
-
-int main(void)
-{
-    /* BEGIN TEST: */
-eventfd_t value;
-int fd = eventfd(0, EFD_CLOEXEC);
-eventfd_read(fd, &value);
-eventfd_write(fd, value);
-    /* END TEST: */
-    return 0;
-}
-")
-
 # futimens
 qt_config_compile_test(futimens
     LABEL "futimens()"
@@ -501,10 +483,6 @@ qt_feature("dladdr" PRIVATE
     LABEL "dladdr"
     CONDITION QT_FEATURE_dlopen AND TEST_dladdr
 )
-qt_feature("eventfd" PRIVATE
-    LABEL "eventfd"
-    CONDITION NOT WASM AND TEST_eventfd
-)
 qt_feature("futimens" PRIVATE
     LABEL "futimens()"
     CONDITION NOT WIN32 AND TEST_futimens

src/corelib/kernel/qeventdispatcher_unix.cpp

@@ -19,8 +19,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#if QT_CONFIG(eventfd)
+#if __has_include(<sys/eventfd.h>)
 #  include <sys/eventfd.h>
+static constexpr bool UsingEventfd = true;
+#else
+static constexpr bool UsingEventfd = false;
 #endif
 
 #if defined(Q_OS_VXWORKS)
@@ -54,7 +57,7 @@ QThreadPipe::~QThreadPipe()
     if (fds[0] >= 0)
         close(fds[0]);
 
-    if (!QT_CONFIG(eventfd) && fds[1] >= 0)
+    if (!UsingEventfd && fds[1] >= 0)
         close(fds[1]);
 
 #if defined(Q_OS_VXWORKS)
@@ -104,10 +107,10 @@ bool QThreadPipe::init()
     fds[1] = fds[0];
 #else
     int ret;
-#  if QT_CONFIG(eventfd)
+#  ifdef EFD_CLOEXEC
     ret = fds[0] = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
 #  endif
-    if (!QT_CONFIG(eventfd))
+    if (!UsingEventfd)
         ret = qt_safe_pipe(fds, O_NONBLOCK);
     if (ret == -1) {
         perror("QThreadPipe: Unable to create pipe");
@@ -126,7 +129,7 @@ pollfd QThreadPipe::prepare() const
 void QThreadPipe::wakeUp()
 {
     if ((wakeUps.fetchAndOrAcquire(1) & 1) == 0) {
-#if QT_CONFIG(eventfd)
+#  ifdef EFD_CLOEXEC
         eventfd_write(fds[0], 1);
         return;
 #endif
@@ -149,11 +152,11 @@ int QThreadPipe::check(const pollfd &pfd)
         ::read(fds[0], c, sizeof(c));
         ::ioctl(fds[0], FIOFLUSH, 0);
 #else
-#  if QT_CONFIG(eventfd)
+#  ifdef EFD_CLOEXEC
         eventfd_t value;
         eventfd_read(fds[0], &value);
 #  endif
-        if (!QT_CONFIG(eventfd)) {
+        if (!UsingEventfd) {
             while (::read(fds[0], c, sizeof(c)) > 0) {}
         }
 #endif

src/corelib/qt_cmdline.cmake

@@ -2,7 +2,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 qt_commandline_option(doubleconversion TYPE enum VALUES no qt system)
-qt_commandline_option(eventfd TYPE boolean)
 qt_commandline_option(glib TYPE boolean)
 qt_commandline_option(icu TYPE boolean)
 qt_commandline_option(inotify TYPE boolean)