CMake: remove "res_ninit" feature and collapse to just "libresolv"

Testing for "res_ninit" when WrapResolv.cmake has already checked for
far more complex functions was pointless. Instead, just accept the
library that was found by find_package() as good enough and rename the
feature as "libresolv".

Amends 4a46ba1209907796f4a14f6feb35ed4d70155d7d and
68b625901f9eb7c34e3d7aa302e1c0a454d3190b.

Change-Id: Ib5ce7a497e034ebabb2cfffd1762c0afa2fac6e0
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/CMakeLists.txt

@@ -213,7 +213,7 @@ qt_internal_extend_target(Network CONDITION APPLE
         ${FWCFNetwork}
 )
 
-qt_internal_extend_target(Network CONDITION QT_FEATURE_dnslookup AND TEST_res_ninit
+qt_internal_extend_target(Network CONDITION QT_FEATURE_dnslookup AND QT_FEATURE_libresolv
     SOURCES
         kernel/qdnslookup_unix.cpp
     LIBRARIES
@@ -225,7 +225,7 @@ qt_internal_extend_target(Network CONDITION QT_FEATURE_dnslookup AND WIN32
         kernel/qdnslookup_win.cpp
 )
 
-qt_internal_extend_target(Network CONDITION QT_FEATURE_dnslookup AND NOT TEST_res_ninit AND NOT WIN32
+qt_internal_extend_target(Network CONDITION QT_FEATURE_dnslookup AND NOT QT_FEATURE_libresolv AND NOT WIN32
     SOURCES
         kernel/qdnslookup_dummy.cpp
 )

src/network/configure.cmake

@@ -100,25 +100,6 @@ ci.ifa_prefered = ci.ifa_valid = 0;
 }
 ")
 
-# res_ninit
-qt_config_compile_test(res_ninit
-    LABEL "res_ninit()"
-    LIBRARIES
-        WrapResolv::WrapResolv
-    CODE
-"#include <sys/types.h>
-#include <netinet/in.h>
-#include <resolv.h>
-int main()
-{
-    res_state state;
-    res_ninit(state);
-    res_nclose(state);
-    return 0;
-}
-"
-)
-
 # res_setserver
 qt_config_compile_test(res_setservers
     LABEL "res_setservers()"
@@ -240,6 +221,11 @@ qt_feature("ipv6ifname" PUBLIC
     CONDITION TEST_ipv6ifname
 )
 qt_feature_definition("ipv6ifname" "QT_NO_IPV6IFNAME" NEGATE VALUE "1")
+qt_feature("libresolv" PRIVATE
+    LABEL "libresolv"
+    CONDITION WrapResolv_FOUND
+    AUTODETECT UNIX
+)
 qt_feature("libproxy" PRIVATE
     LABEL "libproxy"
     AUTODETECT OFF
@@ -249,14 +235,9 @@ qt_feature("linux-netlink" PRIVATE
     LABEL "Linux AF_NETLINK"
     CONDITION LINUX AND NOT ANDROID AND TEST_linux_netlink
 )
-qt_feature("res_ninit" PRIVATE
-    LABEL "res_ninit()"
-    CONDITION TEST_res_ninit
-    AUTODETECT UNIX
-)
 qt_feature("res_setservers" PRIVATE
     LABEL "res_setservers()"
-    CONDITION QT_FEATURE_res_ninit AND TEST_res_setservers
+    CONDITION QT_FEATURE_libresolv AND TEST_res_setservers
 )
 qt_feature("securetransport" PUBLIC
     LABEL "SecureTransport"

src/network/kernel/qdnslookup_unix.cpp

@@ -11,7 +11,7 @@
 #include <private/qnativesocketengine_p.h>      // for setSockAddr
 #include <private/qtnetwork-config_p.h>
 
-QT_REQUIRE_CONFIG(res_ninit);
+QT_REQUIRE_CONFIG(libresolv);
 
 #include <sys/types.h>
 #include <netinet/in.h>

src/network/kernel/qhostinfo_unix.cpp

@@ -49,7 +49,7 @@ static void maybeRefreshResolver()
     return;
 #endif
 
-#if QT_CONFIG(res_ninit)
+#if QT_CONFIG(libresolv)
     // OSes known or thought to reach here: AIX, NetBSD, Solaris,
     // Linux with MUSL (though res_init() does nothing and is unnecessary)
 
@@ -92,7 +92,7 @@ QHostInfo QHostInfoAgent::fromName(const QString &hostName)
 
 QString QHostInfo::localDomainName()
 {
-#if QT_CONFIG(res_ninit)
+#if QT_CONFIG(libresolv)
     auto domainNameFromRes = [](res_state r) {
         QString domainName;
         if (r->defdname[0])
@@ -111,7 +111,7 @@ QString QHostInfo::localDomainName()
     // using thread-unsafe version
     maybeRefreshResolver();
     return domainNameFromRes(&_res);
-#endif  // !QT_CONFIG(res_ninit)
+#endif  // !QT_CONFIG(libresolv)
 
     // nothing worked, try doing it by ourselves:
     QFile resolvconf;

tests/auto/network/kernel/CMakeLists.txt

@@ -1,7 +1,7 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
-if(WIN32 OR TEST_res_ninit)
+if(QT_FEATURE_qdnslookup)
     add_subdirectory(qdnslookup)
     add_subdirectory(qdnslookup_appless)
 endif()