Make perlio line buffer VMS record-oriented files on output.

When perlio flushes down to the unix layer, it can introduce a
spurious record boundary when writing to a record-oriented file.
Perl may create such files when doing edit-in-place or any other
context where the file format is inherited from a previous
version of the file.

The problem can be eliminated by enabling line buffering on such
files when they are opened.  This was a regression in 5.10.0 since
before that stdio's buffering performed the same function.

N.B.  Lines longer than the size of the perlio buffer will still
result in multiple records -- a larger buffer may be necessary.

For more details and discussion see:

http://www.nntp.perl.org/group/perl.vmsperl/2010/11/msg15419.html

Thanks to Martin Zinser for the problem report.

1 files changed, 16 insertions, 0 deletions

diff --git a/perlio.c b/perlio.c
index 13b135181d..4620ecd97f 100644
--- a/perlio.c
+++ b/perlio.c
@@ -3761,6 +3761,22 @@ PerlIOBuf_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 		 */
 		PerlLIO_setmode(fd, O_BINARY);
 #endif
+#ifdef VMS
+#include <rms.h>
+		/* Enable line buffering with record-oriented regular files
+		 * so we don't introduce an extraneous record boundary when
+		 * the buffer fills up.
+		 */
+		if (PerlIOBase(f)->flags & PERLIO_F_CANWRITE) {
+		    Stat_t st;
+		    if (PerlLIO_fstat(fd, &st) == 0
+		        && S_ISREG(st.st_mode)
+		        && (st.st_fab_rfm == FAB$C_VAR 
+			    || st.st_fab_rfm == FAB$C_VFC)) {
+			PerlIOBase(f)->flags |= PERLIO_F_LINEBUF;
+		    }
+		}
+#endif
 	    }
 	}
     }