don't bother testing if we can flush all handles when fflush(stdin)

shows the pipe bug

p4raw-id: //depot/perl@5676

diff --git a/Configure b/Configure
index 40a6169..053f227 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -12577,7 +12577,7 @@ main(int argc, char **argv)
         fprintf(stdout, "%s", buf);
         fflush(NULL);
         if (i == -1)
-       return 0;
+           return 0;
         bp = buf;
     }
 }
@@ -12599,7 +12599,7 @@ EOM
                         fflushNULL="$undef"
                     fi
                 fi
-               $rm -f core tryp.core core.tryp.*
+               $rm -f core tryp.c tryp.core core.tryp.*
                ;;
        '')     $cat >&4 <<EOM
 Your fflush(NULL) isn't working (contrary to ANSI C).
@@ -12621,57 +12621,100 @@ $define|true|[yY]*)
        fflushNULL="$undef"
        ;;
 esac
-: check explicit looping only if NULL did not work
+: check explicit looping only if NULL did not work, and if the pipe
+: bug does not show up on an explicit flush too
 case "$fflushNULL" in
 "$undef")
-       : check for fflush all behaviour
-       case "$fflushall" in
-       '')     set try -DTRY_FFLUSH_ALL $output
-               if eval $compile; then
-                       $cat >&4 <<EOM
-(Now testing the other method--but note that also this may fail.)
+       $cat >tryp.c <<EOCP
+#include <stdio.h>
+int
+main(int argc, char **argv)
+{
+    char buf[1024];
+    int i;
+    char *bp = buf;
+    while (1) {
+       while ((i = getc(stdin)) != -1
+              && (*bp++ = i) != '\n'
+              && bp < &buf[1024])
+       /* DO NOTHING */ ;
+       *bp = '\0';
+       fprintf(stdout, "%s", buf);
+       fflush(stdin);
+       if (i == -1)
+           return 0;
+       bp = buf;
+    }
+}
+EOCP
+       set tryp
+       if eval $compile; then
+           $rm -f tryp.out
+           $cat tryp.c | ./tryp$exe_ext 2>/dev/null > tryp.out
+           if cmp tryp.c tryp.out >/dev/null 2>&1; then
+              $cat >&4 <<EOM
+Good, at least fflush(stdin) seems to behave okay when stdin is a pipe.
 EOM
-                       $rm -f try.out
-                       ./try$exe_ext 2>/dev/null
-                       if $test -s try.out -a "X$?" = X42; then
-                               fflushall="`$cat try.out`"
-                       fi
-               fi
-               $rm -f core try.core core.try.*
+               : now check for fflushall behaviour
                case "$fflushall" in
-               x)      $cat >&4 <<EOM
+               '')     set try -DTRY_FFLUSH_ALL $output
+                       if eval $compile; then
+                               $cat >&4 <<EOM
+(Now testing the other method--but note that this also may fail.)
+EOM
+                               $rm -f try.out
+                               ./try$exe_ext 2>/dev/null
+                               if $test -s try.out -a "X$?" = X42; then
+                                       fflushall="`$cat try.out`"
+                               fi
+                       fi
+                       $rm -f core try.core core.try.*
+                       case "$fflushall" in
+                       x)      $cat >&4 <<EOM
 Whew. Flushing explicitly all the stdio streams works.
 EOM
-                       fflushall="$define"
-                       ;;
-               '')     $cat >&4 <<EOM
+                               fflushall="$define"
+                               ;;
+                       '')     $cat >&4 <<EOM
 Sigh. Flushing explicitly all the stdio streams doesn't work.
 EOM
-                       fflushall="$undef"
-                       ;;
-               *)      $cat >&4 <<EOM
+                               fflushall="$undef"
+                               ;;
+                       *)      $cat >&4 <<EOM
 Cannot figure out whether flushing stdio streams explicitly works or not.
 I'm assuming it doesn't.
 EOM
+                               fflushall="$undef"
+                               ;;
+                       esac
+                       ;;
+               "$define"|true|[yY]*)
+                       fflushall="$define"
+                       ;;
+               *)
                        fflushall="$undef"
                        ;;
                esac
-               ;;
-       "$define"|true|[yY]*)
-               fflushall="$define"
-               ;;
-       *)
+           else
+               $cat >&4 <<EOM
+All is futile.  Even fflush(stdin) clobbers input pipes!
+EOM
                fflushall="$undef"
-               ;;
-       esac
+           fi
+       else
+           fflushall="$undef"
+       fi
+       $rm -f core tryp.c tryp.core core.tryp.*
        ;;
-*)     fflushall="$undef"      
+*)     fflushall="$undef"
        ;;
 esac
+
 case "$fflushNULL$fflushall" in
 undefundef)
        $cat <<EOM
-I cannot figure out how to flush pending stdio output.
+OK, I give up.  I cannot figure out how to flush pending stdio output.
+We won't be flushing handles at all before fork/exec/popen.
 EOM
        ;;
 esac