Pass the correct stat to backup filesHEADmaster

The last case to call output_file() in the main loop is
    output_file (outname, NULL, &tmpoutst, NULL, NULL,
                 file_type | 0, backup);
and this essentially means to create a backup file (where to=NULL)
only if backup=true, and does nothing else.

And, in the current code, the passed file stat (&tmpoutst) is a file
stat of the temporary file that has been processed, not the original
file (outname) to be backed up.  When the backup is performed
immediately, this is no big problem.  However, output_file() may
schedule the deferred handling, and the given file may be backed up at
a later point.  The problem is that create_backup() tries to avoid the
backup of the same file twice, and it checks the given stat i-node
number in the hash list.  Since it's a stat of a temporary file, the
same i-node number may be reused once a temp file is deleted and
another is created.  This results in a false-positive detection of the
already existing file, eventually missing a backup file.

This patch attempts to address the issue:
- Modify the condition for better understanding, clearly indicating
  that the code there is for creating a backup file
- Pass the stat of the original file instead of a temporary file

BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1198106
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jean Delvare <jdelvare@suse.de>

1 files changed, 10 insertions, 3 deletions

diff --git a/src/patch.c b/src/patch.c
index 73d140f..d5f456c 100644
--- a/src/patch.c
+++ b/src/patch.c
@@ -622,9 +622,16 @@ main (int argc, char **argv)
 			output_file (NULL, NULL, NULL, inname, &instat,
 				     mode, backup);
 		    }
-		  else
-		    output_file (outname, NULL, &tmpoutst, NULL, NULL,
-				 file_type | 0, backup);
+		  else if (backup)
+		    {
+		      struct stat outstat;
+
+		      if (stat_file (outname, &outstat) != 0)
+			say ("Cannot stat file %s, skipping backup\n", outname);
+		      else
+			output_file (outname, NULL, &outstat, NULL, NULL,
+				     file_type | 0, true);
+		    }
 		}
 	    }
       }