A fix of sorts for the flush-before-dup scenario.

p4raw-id: //depot/cfgperl@3997

1 files changed, 10 insertions, 1 deletions

diff --git a/doio.c b/doio.c
index 8610a149d8..413e342dbc 100644
--- a/doio.c
+++ b/doio.c
@@ -283,8 +283,17 @@ Perl_do_open9(pTHX_ GV *gv, register char *name, I32 len, int as_raw,
 			}
 			if (IoIFP(thatio)) {
 			    PerlIO *fp = IoIFP(thatio);
-				/* Flush stdio buffer before dup */
+			    /* Flush stdio buffer before dup. --mjd
+			     * Unfortunately SEEK_CURing 0 seems to
+			     * be optimized away on most platforms;
+			     * only Solaris and Linux seem to flush
+			     * on that. --jhi */
 			    PerlIO_seek(fp, 0, SEEK_CUR);
+			    /* On the other hand, do all platforms
+			     * take gracefully to flushing a read-only
+			     * filehandle?  Perhaps we should do
+			     * fsetpos(src)+fgetpos(dst)?  --nik */
+			    PerlIO_flush(fp);
 			    fd = PerlIO_fileno(fp);
 			    if (IoTYPE(thatio) == 's')
 				IoTYPE(io) = 's';