win32: improved results for symlinks from stat(2)

The file size and times reported when Windows follows a symlink
are incorrect.  To get the correct values canonicalize the path
and try again.

Also fetch the correct device id and inode for symlinks.

1 files changed, 56 insertions, 36 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 9d9935f4b..11cef0abe 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -138,6 +138,7 @@ int err_win_to_posix(DWORD winerr)
         case ERROR_WAIT_NO_CHILDREN: error = ECHILD; break;
         case ERROR_WRITE_FAULT: error = EIO; break;
         case ERROR_WRITE_PROTECT: error = EROFS; break;
+        case ERROR_CANT_RESOLVE_FILENAME: error = ELOOP; break;
         }
         return error;
 }
@@ -480,60 +481,80 @@ static uid_t file_owner(HANDLE fh)
 }
 #endif
 
+static int is_symlink(DWORD attr, const char *pathname, WIN32_FIND_DATAA *fbuf)
+{
+        if (attr & FILE_ATTRIBUTE_REPARSE_POINT) {
+                HANDLE handle = FindFirstFileA(pathname, fbuf);
+                if (handle != INVALID_HANDLE_VALUE) {
+                        FindClose(handle);
+                        return ((fbuf->dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
+                                        fbuf->dwReserved0 == IO_REPARSE_TAG_SYMLINK);
+                }
+        }
+        return 0;
+}
+
 /* If follow is true then act like stat() and report on the link
  * target. Otherwise report on the link itself.
  */
 static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
 {
-        int err;
+        int err = EINVAL;
         WIN32_FILE_ATTRIBUTE_DATA fdata;
+        WIN32_FIND_DATAA findbuf;
 #if ENABLE_FEATURE_EXTRA_FILE_DATA
+        DWORD flags;
         BY_HANDLE_FILE_INFORMATION hdata;
         HANDLE fh;
 #endif
 
-        if (!(err = get_file_attr(file_name, &fdata))) {
+        while (file_name && !(err=get_file_attr(file_name, &fdata))) {
                 buf->st_ino = 0;
                 buf->st_uid = DEFAULT_UID;
                 buf->st_gid = DEFAULT_GID;
-                buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
-                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 : 1;
-                if (S_ISREG(buf->st_mode) &&
-                                (has_exe_suffix(file_name) || has_exec_format(file_name)))
-                        buf->st_mode |= S_IXUSR|S_IXGRP|S_IXOTH;
-                buf->st_size = fdata.nFileSizeLow |
-                        (((off64_t)fdata.nFileSizeHigh)<<32);
-                buf->st_dev = buf->st_rdev = 0; /* not used by Git */
-                buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
-                buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
-                buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
-                if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
-                        WIN32_FIND_DATAA findbuf;
-                        HANDLE handle = FindFirstFileA(file_name, &findbuf);
-                        if (handle != INVALID_HANDLE_VALUE) {
-                                if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
-                                                (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) {
-                                        if (follow) {
-                                                char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
-                                                buf->st_size = readlink(file_name, buffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
-                                        } else {
-                                                buf->st_mode = S_IFLNK;
-                                        }
-                                        buf->st_mode |= S_IRUSR|S_IRGRP|S_IROTH;
-                                        if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
-                                                buf->st_mode |= S_IWUSR|S_IWGRP;
-                                }
-                                FindClose(handle);
+                buf->st_dev = buf->st_rdev = 0;
+
+                if (is_symlink(fdata.dwFileAttributes, file_name, &findbuf)) {
+                        char *name = auto_string(xmalloc_realpath(file_name));
+
+                        if (follow) {
+                                /* The file size and times are wrong when Windows follows
+                                 * a symlink.  Use the canonicalized path to try again. */
+                                err = errno;
+                                file_name = name;
+                                continue;
                         }
+
+                        /* Get the contents of a symlink, not its target. */
+                        buf->st_mode = S_IFLNK|S_IRWXU|S_IRWXG|S_IRWXO;
+                        buf->st_size = name ? strlen(name) : 0; /* should use readlink */
+                        buf->st_atime = filetime_to_time_t(&(findbuf.ftLastAccessTime));
+                        buf->st_mtime = filetime_to_time_t(&(findbuf.ftLastWriteTime));
+                        buf->st_ctime = filetime_to_time_t(&(findbuf.ftCreationTime));
                 }
+                else {
+                        /* The file is not a symlink. */
+                        buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
+                        if (S_ISREG(buf->st_mode) &&
+                                        (has_exe_suffix(file_name) || has_exec_format(file_name)))
+                                buf->st_mode |= S_IXUSR|S_IXGRP|S_IXOTH;
+                        buf->st_size = fdata.nFileSizeLow |
+                                (((off64_t)fdata.nFileSizeHigh)<<32);
+                        buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
+                        buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
+                        buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
+                }
+                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 : 1;
 
 #if ENABLE_FEATURE_EXTRA_FILE_DATA
+                flags = FILE_FLAG_BACKUP_SEMANTICS;
+                if (S_ISLNK(buf->st_mode))
+                        flags |= FILE_FLAG_OPEN_REPARSE_POINT;
 #if ENABLE_FEATURE_IDENTIFY_OWNER
                 fh = CreateFile(file_name, READ_CONTROL, 0, NULL,
-                                                        OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+                                                        OPEN_EXISTING, flags, NULL);
 #else
-                fh = CreateFile(file_name, 0, 0, NULL, OPEN_EXISTING,
-                                                        FILE_FLAG_BACKUP_SEMANTICS, NULL);
+                fh = CreateFile(file_name, 0, 0, NULL, OPEN_EXISTING, flags, NULL);
 #endif
                 if (fh != INVALID_HANDLE_VALUE) {
                         if (GetFileInformationByHandle(fh, &hdata)) {
@@ -987,9 +1008,8 @@ static char *resolve_symlinks(char *path)
                 return NULL;
 
         /* need a file handle to resolve symlinks */
-        h = CreateFileA(path, GENERIC_READ, FILE_SHARE_READ, NULL,
-                        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL|FILE_FLAG_BACKUP_SEMANTICS,
-                        NULL);
+        h = CreateFileA(path, 0, 0, NULL, OPEN_EXISTING,
+                                FILE_FLAG_BACKUP_SEMANTICS, NULL);
         if (h != INVALID_HANDLE_VALUE) {
                 /* normalize the path and return it on success */
                 DWORD status = GetFinalPathNameByHandleA(h, path, MAX_PATH,