bug #41707: RCS 5.8 file corruption when using file descriptor IO for large files

[Achim Gratz]

As described in

https://cygwin.com/ml/cygwin/2012-06/msg00334.html
https://cygwin.com/ml/cygwin/2012-09/msg00331.html

and demonstrated with

https://cygwin.com/ml/cygwin/2013-10/msg00086.html

the STDIO code path fails for work files above a certain size on
Cygwin.  Based on the analysis of how the breakage occurs I've developed
the following patch for your consideration:

--- origsrc/rcs-5.9.2/src/ci.c  2013-10-04 14:01:48.000000000 +0200
+++ src/rcs-5.9.2/src/ci.c      2014-06-18 15:55:34.237014800 +0200
@@ -1085,9 +1085,21 @@ ci_main (const char *cmd, int argc, char
                 *++diffp = NULL;
                 if (DIFF_TROUBLE == runv (wfd, diffname, diffv))
                   RFATAL ("diff failed");
+
+               /* Re-open the work file to sync the notion of the
+                  file position and the memory buffer.  These may
+                  have drifted apart due to sharing the fd with the
+                  diff subprocess.  */
+               fro_zclose (&work.fro);
+               if (!(work.fro = fro_open (mani_filename, FOPEN_R_WORK, 
&work.st)))
+                 {
+                   syserror_errno (mani_filename);
+                   continue;
+                 }
+
                 if (newhead)
                   {
                     fro_bob (work.fro);
                     putdftext (&bud.d, work.fro, frew, false);
                     if (!putdtext (bud.target, diffname, frew, true))
                       continue;
--- origsrc/rcs-5.9.2/tests/Makefile.am 2013-04-20 20:08:38.000000000 +0200
+++ src/rcs-5.9.2/tests/Makefile.am     2014-06-18 11:28:41.593056000 +0200
@@ -79,6 +79,7 @@ TESTS = \
  t802 \
  t803 \
  t810 \
+ t820 \
  t900 \
  t999
 
--- origsrc/rcs-5.9.2/tests/btdt.c      2013-10-04 13:45:57.000000000 +0200
+++ src/rcs-5.9.2/tests/btdt.c  2014-06-18 10:35:51.159400500 +0200
@@ -164,6 +164,7 @@ main (int argc, char *argv[argc])
 
   if (2 > argc || STR_SAME ("--help", argv[1]))
     {
+    HELP:
       printf ("Usage: %s COMPONENT [ARG...]\n", me);
       for (size_t i = 0; i < NYEAH; i++)
         printf ("- %-10s %s\n", yeah[i].component, yeah[i].usage);
@@ -178,7 +179,7 @@ main (int argc, char *argv[argc])
       printf ("License GPLv3+; GNU GPL version 3 or later"
               " <http://gnu.org/licenses/gpl.html>\n\n");
       argv[1] = "--help";
-      return main (argc, argv);
+      goto HELP;
     }
 
   for (size_t i = 0; i < NYEAH; i++)
--- origsrc/rcs-5.9.2/tests/t820        1970-01-01 01:00:00.000000000 +0100
+++ src/rcs-5.9.2/tests/t820    2014-06-18 14:49:02.911300700 +0200
@@ -0,0 +1,60 @@
+# t820 --- RM_STDIO codepath
+#
+# Copyright (C) 2013 Thien-Thi Nguyen
+#
+# This program is free software: you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation, either version 3 of
+# the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty
+# of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. $srcdir/common
+split_std_out_err no
+unset TMPDIR
+
+##
+# Check that using the RM_STDIO code path
+# doesn't truncate the work file on Cygwin.
+# This test derives from a 5.8 regression.
+##
+
+##
+# NB: We jam env ‘RCS_MEM_LIMIT=0’ to force stdio operation.
+##
+RCS_MEM_LIMIT=0
+export RCS_MEM_LIMIT
+
+cd $wd
+    set -x
+    pwd
+    mkdir RCS
+    for n in 65535 65536 65537 262143 262144 262150 262140 262142 262145
+    do
+        rm -f RCS/foo,v
+        # Check in initial revision (1.1), with small contents.
+        echo foo > foo
+        ci -l foo < /dev/null
+        must [ 4 == $(co -p foo | wc -c) ]
+        # Check in second revision (1.2), size $n bytes.
+        # Note, adding "-f" to the ci command prevents the bug.
+        yes | head -${n}c > foo
+        ci -m"blafasel" -l foo
+        cp -f RCS/foo,v RCS/foo,v.$n
+        # When n=262143, the following gives 262143 (correct);
+        # when n=262144, the following gives 65535 (wrong).
+        must [ $n == $(co -p foo | wc -c) ]
+        # The following succeeds with n=262143, but fails with n=262144:
+        #   co: RCS/foo,v:32805: edit script refers to line past end of file
+        #   co aborted
+        must co -p1.1 foo > /dev/null
+    done
+cd ..
+
+# t820 ends here


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

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