From 22e8af32f318dd1361ee58c34baae9f3e2fdb93f Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 24 Oct 2017 08:26:26 -0600
Subject: [PATCH] Windows: avoid loop on reparse-point cycles

In Windows 10 Fall Creators Update, a OneDrive mount looks to Racket like
a reparse point that refers to itself. Make Racket stop trying to resolve
the path further in that case.

Relevant to #1671
---
 racket/src/rktio/rktio_fs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/racket/src/rktio/rktio_fs.c b/racket/src/rktio/rktio_fs.c
index 6841b46375..f78973de8f 100644
--- a/racket/src/rktio/rktio_fs.c
+++ b/racket/src/rktio/rktio_fs.c
@@ -349,6 +349,7 @@ static int UNC_stat(rktio_t *rktio, const char *dirname, int *flags, int *isdir,
   char *copy;
   WIN32_FILE_ATTRIBUTE_DATA fad;
   int len, must_be_dir = 0;
+  int same_path = 0; /* to give up on cyclic links */
   const wchar_t *wp;
 
   if (resolved_path)
@@ -420,7 +421,7 @@ static int UNC_stat(rktio_t *rktio, const char *dirname, int *flags, int *isdir,
     free(copy);
     return 0;
   } else {
-    if (GET_FF_ATTRIBS(fad) & FF_A_LINK) {
+    if ((GET_FF_ATTRIBS(fad) & FF_A_LINK) && !same_path) {
       if (islink) {
 	*islink = 1;
 	return 1;
@@ -465,6 +466,8 @@ static int UNC_stat(rktio_t *rktio, const char *dirname, int *flags, int *isdir,
 	if (resolved_path)
 	  *resolved_path = dirname;
 
+	same_path = !strcmp(dirname, copy);
+
         free(dest);
         free(copy);