https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=827743ab7684a09bc077c91f6206e16ea85881b4
commit 827743ab7684a09bc077c91f6206e16ea85881b4
Author: Johannes Schindelin <johannes.schinde...@gmx.de>
AuthorDate: Fri Jun 20 12:03:11 2025 +0200
Commit: Corinna Vinschen <cori...@vinschen.de>
CommitDate: Mon Jun 23 10:31:24 2025 +0200
Cygwin: symlink_native: allow linking to `..`
When running
CYGWIN=winsymlinks:nativestrict ln -s .. abc
the counter-intuitive result is _not_ a symbolic link to `..`, but
instead to `../../$(basename "$PWD")`.
The reason for this is that the search for the longest common prefix
assumes that the link target is not a strict prefix of the parent
directory of the link itself.
Let's fix that.
Signed-off-by: Johannes Schindelin <johannes.schinde...@gmx.de>
Diff:
---
winsup/cygwin/path.cc | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index d26f99ee7fb8..310876b5accd 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -1855,9 +1855,18 @@ symlink_native (const char *oldpath, path_conv
&win32_newpath)
while (towupper (*++c_old) == towupper (*++c_new))
;
/* The last component could share a common prefix, so make sure we end
- up on the first char after the last common backslash. */
- while (c_old[-1] != L'\\')
- --c_old, --c_new;
+ up on the first char after the last common backslash.
+
+ However, if c_old is a strict prefix of c_new (at a component
+ boundary), or vice versa, then do not try to find the last common
+ backslash. */
+ if ((!*c_old || *c_old == L'\\') && (!*c_new || *c_new == L'\\'))
+ c_old += !!*c_old, c_new += !!*c_new;
+ else
+ {
+ while (c_old[-1] != L'\\')
+ --c_old, --c_new;
+ }
/* 2. Check if prefix is long enough. The prefix must at least points to
a complete device: \\?\X:\ or \\?\UNC\server\share\ are the
minimum
@@ -1882,8 +1891,10 @@ symlink_native (const char *oldpath, path_conv
&win32_newpath)
final_oldpath = &final_oldpath_buf;
final_oldpath->Buffer = tp.w_get ();
PWCHAR e_old = final_oldpath->Buffer;
- while (num-- > 0)
- e_old = wcpcpy (e_old, L"..\\");
+ while (num > 1 || (num == 1 && *c_old))
+ e_old = wcpcpy (e_old, L"..\\"), num--;
+ if (num > 0)
+ e_old = wcpcpy (e_old, L"..");
wcpcpy (e_old, c_old);
}
}
