win32: let stat(2) return correct st_size for symlink

Previously stat(2) set st_size to the length of the canonicalised
symlink target.  Call readlink(2) to get the actual length of the
target string.

1 files changed, 8 insertions, 5 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 95f5e5687..f49d8079d 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -630,6 +630,7 @@ static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
         WIN32_FIND_DATAA findbuf;
         DWORD low, high;
         off64_t size;
+        ssize_t len;
 #if ENABLE_FEATURE_EXTRA_FILE_DATA
         DWORD flags;
         BY_HANDLE_FILE_INFORMATION hdata;
@@ -645,20 +646,19 @@ static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
                         get_symlink_data(fdata.dwFileAttributes, file_name, &findbuf);
 
                 if (buf->st_tag) {
-                        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. */
+                                 * a symlink.  Use the canonicalized path instead. */
                                 err = errno;
-                                file_name = name;
+                                file_name = auto_string(xmalloc_realpath(file_name));
                                 continue;
                         }
 
                         /* Get the contents of a symlink, not its target. */
                         buf->st_mode = S_IFLNK|S_IRWXU|S_IRWXG|S_IRWXO;
                         buf->st_attr = fdata.dwFileAttributes;
-                        buf->st_size = name ? strlen(name) : 0; /* should use readlink */
+                        len = readlink(file_name, NULL, 0);
+                        buf->st_size = len == -1 ? 0 : len;
                         buf->st_atim = filetime_to_timespec(&(findbuf.ftLastAccessTime));
                         buf->st_mtim = filetime_to_timespec(&(findbuf.ftLastWriteTime));
                         buf->st_ctim = filetime_to_timespec(&(findbuf.ftCreationTime));
@@ -1527,6 +1527,7 @@ char *realpath(const char *path, char *resolved_path)
 }
 
 #define SRPB rptr->SymbolicLinkReparseBuffer
+/* Non-standard feature:  if buf is NULL just return the length. */
 ssize_t readlink(const char *pathname, char *buf, size_t bufsiz)
 {
         HANDLE h;
@@ -1554,6 +1555,8 @@ ssize_t readlink(const char *pathname, char *buf, size_t bufsiz)
                 }
 
                 if (name) {
+                        if (buf == NULL)
+                                return len;
                         if (len > bufsiz)
                                 len = bufsiz;
                         len = WideCharToMultiByte(CP_ACP, 0, name, len, buf, bufsiz, 0, 0);