Detect whether fflush(NULL) works as per change #3352.

p4raw-link: @3352 on //depot/perl: 45bc920620377d5a7720d3d562c48df1eb0c2e68

p4raw-id: //depot/cfgperl@3398

diff --git a/Configure b/Configure
index d359877..ec15a53 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -20,7 +20,7 @@
 
 # $Id: Head.U,v 3.0.1.9 1997/02/28 15:02:09 ram Exp $
 #
-# Generated on Wed May 12 01:15:37 EET DST 1999 [metaconfig 3.0 PL70]
+# Generated on Wed May 12 12:24:25 EET DST 1999 [metaconfig 3.0 PL70]
 # (with additional metaconfig patches by perlbug@perl.com)
 
 cat >/tmp/c1$$ <<EOF
@@ -572,6 +572,7 @@ lddlflags=''
 usedl=''
 doublesize=''
 ebcdic=''
+fflushNULL=''
 fpostype=''
 gidtype=''
 groupstype=''
@@ -10917,6 +10918,53 @@ $rm -f tebcdic.c tebcdic
 set ebcdic
 eval $setvar
 
+: check for fflush NULL behaviour
+case "$fflushNULL" in
+'') $cat <<EOM
+
+Checking to see whether fflush(NULL) flushes all pending stdio output...
+EOM
+       $cat >try.c <<EOCP
+#include <stdio.h>
+int main() {
+  FILE* p = fopen("try.out", "w");
+  fputc('x', p);
+  fflush(NULL);
+  _exit(0);
+}
+EOCP
+       set try
+       $rm -f try.out
+       if eval $compile_ok; then
+               case "`$cat try.out`" in
+               x)      cat >&4 <<EOM
+Your fflush(NULL) works okay.
+EOM
+                       fflushNULL=undef
+                       ;;
+               '')     cat >&4 <<EOM
+Your fflush(NULL) isn't working (contrary to ANSI C).
+EOM
+                       fflushNULL=undef
+                       ;;
+               *)      cat >&4 <<EOM
+Cannot figure out whether your fflush(NULL) works or not.
+I'm assuming it doesn't (contrary to ANSI C).
+EOM
+                       fflushNULL=undef
+                       ;;
+               esac
+       fi
+       $rm -f try.* try
+       ;;
+$define|true|[yY]*)
+       fflushNULL=define
+       ;;
+*)
+       fflushNULL=undef
+       ;;
+esac
+
 : see what type file positions are declared as in the library
 rp="What is the type for file position used by fsetpos()?"
 set fpos_t fpostype long stdio.h sys/types.h
@@ -13004,6 +13052,7 @@ eunicefix='$eunicefix'
 exe_ext='$exe_ext'
 expr='$expr'
 extensions='$extensions'
+fflushNULL='$fflushNULL'
 find='$find'
 firstmakefile='$firstmakefile'
 flex='$flex'

diff --git a/config_h.SH b/config_h.SH
index 68dc253..81dfcaa 100644 (file)
--- a/config_h.SH
+++ b/config_h.SH
@@ -2213,6 +2213,12 @@ sed <<!GROK!THIS! >config.h -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un-
  */
 #$usedl USE_DYNAMIC_LOADING            /**/
 
+/* FFLUSH_NULL:
+ *     This symbol, if defined, tells that fflush(NULL) does flush
+ *     all pending stdio output.
+ */
+#$fflushNULL FFLUSH_NULL               /**/
+
 /* DB_Prefix_t:
  *     This symbol contains the type of the prefix structure element
  *     in the <db.h> header file.  In older versions of DB, it was

diff --git a/perl.h b/perl.h
index 5cbecd2..4d8b45c 100644 (file)
--- a/perl.h
+++ b/perl.h
@@ -1455,7 +1455,9 @@ typedef pthread_key_t     perl_key;
  * XXX the default needs a Configure test, as it may not work everywhere.
  */
 #ifndef PERL_FLUSHALL_FOR_CHILD
-#define PERL_FLUSHALL_FOR_CHILD        PerlIO_flush((PerlIO*)NULL)
+# if (defined(USE_STDIO) && defined(FFLUSH_NULL)) || defined(USE_SFIO)
+#  define PERL_FLUSHALL_FOR_CHILD      PerlIO_flush((PerlIO*)NULL)
+# endif
 #endif
 
 /* Some unistd.h's give a prototype for pause() even though