POSIX constants can be set to -1 if the functionnality is unavailable

configure must check the value of a POSIX constant, not just if it's
defined, to determine if a POSIX functionnality is available.

Problem reported by Brian Postow on -devel.

diff --git a/configure b/configure
index 909439ccb8d6397c7f673e186c0f48868150dedc..b0e7028553ab74d2dd6c81f6397d297efba2c8cb 100755 (executable)
--- a/configure
+++ b/configure
@@ -2257,6 +2257,25 @@ CheckDefine()
     CheckForDefine "$def" "$@" || AddDefine "$def" "$decl"
 }
 
+#
+# Look for a #define with a positive value in system include files.
+# This is especially useful for POSIX defines which may be defined
+# to -1 or 0 when the functionnality is not supported.
+#
+CheckForPositiveDefine()
+{
+    def=$1; shift
+    (for i do
+       echo "#include \"$i\""
+     done
+     for i in "#if defined($def) && ($def > 0L)" "FOUND" "#endif"; do
+       echo "$i"
+     done
+    )>t.c
+    capture cat t.c
+    runMakeX t 't:; ${CCF} -E t.c' | grep FOUND >&5
+}
+
 CheckTermioFuncDecls()
 {
     CheckFuncDecl cfsetospeed \
@@ -3137,18 +3156,13 @@ BuildPortDotH()
        Note "... configure use of HP-UX realtime process control interface"
        echo '#define HAS_RTPRIO 1'
     }
-    CheckForDefine _POSIX_PRIORITY_SCHEDULING unistd.h sched.h && {
+    CheckForPositiveDefine _POSIX_PRIORITY_SCHEDULING unistd.h sched.h && {
+       Note "... configure use of POSIX realtime process control interface"
+       echo '#define HAS_POSIXSCHED 1'
        case $TARGET in
-       *darwin8*)      Note "... ignoring POSIX realtime process control interface as invalid";;
-       *darwin9*)      Note "... ignoring POSIX realtime process control interface as invalid";;
-       *)
-                       Note "... configure use of POSIX realtime process control interface"
-                       echo '#define HAS_POSIXSCHED 1'
-                       case $TARGET in
-                       *-*-sco3.2v5.*) echo '#define RT_PRIORITY 96';;
-                       *-linux*)       echo '#define RT_PRIORITY 1';;
-                       *)              echo '#define RT_PRIORITY 1';;
-                       esac
+               *-*-sco3.2v5.*) echo '#define RT_PRIORITY 96';;
+               *-linux*)       echo '#define RT_PRIORITY 1';;
+               *)              echo '#define RT_PRIORITY 1';;
        esac
     }
     CheckForTXCD && {