Print error on useless fdout,fdin options

CHANGES

@@ -213,6 +213,11 @@ corrections:
 	Help for filan -L was bad, is now corrected to:
 	"follow symbolic links instead of showing their properties"
 
+	Address options fdin and fdout were silently ignored when not applicable
+	due to -u or -U option. Now these combinations are caught as errors.
+	Test: FDOUT_ERROR
+	Issue reported by Hendrik.
+
 porting:
 	Red Hat issue 1020203: configure checks fail with some compilers.
 	Use case: clang

test.sh

@@ -12537,6 +12537,39 @@ N=$((N+1))
 done
 
 
+# test if option fdout in write only context issues an error
+NAME=FDOUT_ERROR
+case "$TESTS" in
+*%$N%*|*%functions%*|*%bugs%*|*%socket%*|*%$NAME%*)
+TEST="$NAME: fdout bails out in write-only context"
+# use EXEC in write-only context with option fdout. Expected behaviour: error
+if ! eval $NUMCOND; then :; else
+tf="$td/test$N.stdout"
+te="$td/test$N.stderr"
+tdiff="$td/test$N.diff"
+da="test$N $(date) $RANDOM"
+CMD="$SOCAT $opts -u /dev/null EXEC:cat,fdout=1"
+printf "test $F_n $TEST... " $N
+$CMD >/dev/null 2>"${te}"
+rc=$?
+if [ $rc -eq 1 ]; then
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+else
+    $PRINTF "$FAILED\n"
+    echo "$CMD"
+    cat "${te}"
+    echo "command did not terminate with error!"
+    numFAIL=$((numFAIL+1))
+    listFAIL="$listFAIL $N"
+fi
+fi # NUMCOND
+ ;;
+esac
+PORT=$((PORT+1))
+N=$((N+1))
+
+
 ###############################################################################
 # here come tests that might affect your systems integrity. Put normal tests
 # before this paragraph.

xio-progcall.c

@@ -164,8 +164,17 @@ int _xioopen_progcall(int xioflags,	/* XIO_RDONLY etc. */
    if (!retropt_int(popts, OPT_LEFTFD,  &fdi)) {
       fdo = fdi;
    }
-   retropt_int(popts, OPT_LEFTINFD,  &fdi);
+
-   retropt_int(popts, OPT_LEFTOUTFD, &fdo);
+   if (retropt_int(popts, OPT_LEFTINFD,  (unsigned short *)&fdi) >= 0) {
+      if ((xioflags&XIO_ACCMODE) == XIO_RDONLY) {
+	 Error("_xioopen_progcall(): option fdin is useless in read-only mode");
+      }
+   }
+   if (retropt_int(popts, OPT_LEFTOUTFD, (unsigned short *)&fdo) >= 0) {
+      if ((xioflags&XIO_ACCMODE) == XIO_WRONLY) {
+	 Error("_xioopen_progcall(): option fdout is useless in write-only mode");
+      }
+   }
 
    if (!retropt_int(popts, OPT_RIGHTFD,  &rightin)) {
       rightout = rightin;