win32(symlink): fix logic to determine the type of the symlink

On Windows, there are file symlinks and directory symlinks. When trying
to `opendir()` a symlink marked as `file`, it will fail. Even if the
target is a directory. Because it's the wrong symlink type.

To address this, our `symlink()` function calls `stat(target, ...)` to
see whether the target exists and is a directory.

The problem is that this `target` can be a relative path, and the link
path can _also_ be a relative path. Example: `symlink("dir", "uh/oh")`.
In this example, the target might say `dir`, but it is relative to
`uh/oh`, i.e. we need to `stat("uh/dir", ...)`.

This is necessary to pass the `cp` tests because they first create such
a directory symlink and then try to copy it while dereferencing
symlinks, i.e. calling `opendir()` on the symlink.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

1 files changed, 10 insertions, 1 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index c9b72ae98..2e9a53393 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1076,13 +1076,22 @@ int symlink(const char *target, const char *linkpath)
         DWORD flag = SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
         struct stat st;
         DECLARE_PROC_ADDR(BOOL, CreateSymbolicLinkA, LPCSTR, LPCSTR, DWORD);
+        char *relative = NULL;
 
         if (!INIT_PROC_ADDR(kernel32.dll, CreateSymbolicLinkA)) {
                 return -1;
         }
 
-        if (stat(target, &st) != -1 && S_ISDIR(st.st_mode))
+        if (!is_absolute_path(target) && has_path(linkpath)) {
+                /* make target's path relative to current directory */
+                const char *name = bb_get_last_path_component_nostrip(linkpath);
+                relative = xasprintf("%.*s%s",
+                                                (int)(name - linkpath), linkpath, target);
+        }
+
+        if (stat(relative ?: target, &st) != -1 && S_ISDIR(st.st_mode))
                 flag |= SYMBOLIC_LINK_FLAG_DIRECTORY;
+        free(relative);
 
  retry:
         if (!CreateSymbolicLinkA(linkpath, target, flag)) {