From a9671a77476b0dac171cf5ba1f9882fd66a4e038 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Wolfgang=20St=C3=B6ggl?= <c72578@yahoo.de>
Date: Fri, 18 Jan 2019 18:05:47 +0100
Subject: [PATCH] Fix: Cannot rename temporary file to final file

- Fixes the following failing tests under Windows:
  modify1, modify2, modify3, modify4, modify5
- Use CreateFileA() with FILE_SHARE_DELETE in rrd_open.c,
  so that the outfilename can later be replaced by tmpfilename using
  write_rrd() in rrd_create.c
---
 src/rrd_create.c | 23 ++++++++++++++++++++---
 src/rrd_open.c   | 16 ++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/rrd_create.c b/src/rrd_create.c
index 464073b7..32e9ce2f 100644
--- a/src/rrd_create.c
+++ b/src/rrd_create.c
@@ -1482,13 +1482,30 @@ int write_rrd(
             }
 
 #ifdef WIN32
-/* in windows, renaming to an existing file is verboten */
-            unlink(outfilename);
-#endif
+/* In Windows, renaming to an existing file is not allowed. Even, if the file
+ * is deleted before, using _unlink() here. Furthermore the FILE_SHARE_DELETE
+ * flag is required, which is used in CreateFileA in rrd_open.c
+ * Check first, if the file exists. Use ReplaceFileA if the file exists.
+ * Otherwise rename as usual */
+            if (_access_s(outfilename, 0) == 0) {
+                if (ReplaceFileA(outfilename, tmpfilename, NULL, 0, 0, 0) ==
+                    0) {
+                    rrd_set_error("Cannot replace %s!", outfilename);
+                    goto done;
+                }
+            } else {
+                if (rename(tmpfilename, outfilename) != 0) {
+                    rrd_set_error
+                        ("Cannot rename temporary file to final file!");
+                    goto done;
+                }
+            }
+#else
             if (rename(tmpfilename, outfilename) != 0) {
                 rrd_set_error("Cannot rename temporary file to final file!");
                 goto done;
             }
+#endif
 
             // after the rename: forget the file again, just to be sure...
             if (rrdc_is_any_connected()) {
diff --git a/src/rrd_open.c b/src/rrd_open.c
index 03377710..d02acfe2 100644
--- a/src/rrd_open.c
+++ b/src/rrd_open.c
@@ -270,10 +270,26 @@ rrd_file_t *rrd_open(
     flags |= O_BINARY;
 #endif
 
+#if defined(_WIN32)
+    /* In Windows we need FILE_SHARE_DELETE, so that the file can be
+     * renamed/replaced later on in rrd_create.c
+     * This is only possible using CreateFileA() first and not using open() alone */
+    HANDLE    handle;
+
+    handle =
+        CreateFileA(file_name, GENERIC_READ | GENERIC_WRITE,
+                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                    NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+    if ((rrd_simple_file->fd = _open_osfhandle((intptr_t) handle, flags)) < 0) {
+        rrd_set_error("opening '%s': %s", file_name, rrd_strerror(errno));
+        goto out_free;
+    }
+#else
     if ((rrd_simple_file->fd = open(file_name, flags, 0666)) < 0) {
         rrd_set_error("opening '%s': %s", file_name, rrd_strerror(errno));
         goto out_free;
     }
+#endif
 
 #ifdef HAVE_MMAP
 #ifdef HAVE_BROKEN_MS_ASYNC
-- 
2.47.2