From f037641e70bbdd1e9037a4b07c3826af027808a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Steffen=20Schu=CC=88mann?= <s.schuemann@pobox.com>
Date: Sun, 19 Jul 2026 11:19:46 +0200
Subject: [PATCH] Work on handling of relative symlinks on Windows, refs #211

---
 include/ghc/filesystem.hpp | 22 +++++++++++++++-------
 test/filesystem_test.cpp   | 12 ++++++++++++
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/include/ghc/filesystem.hpp b/include/ghc/filesystem.hpp
index c10f810..696d2e4 100644
--- a/include/ghc/filesystem.hpp
+++ b/include/ghc/filesystem.hpp
@@ -2199,7 +2199,7 @@ GHC_INLINE std::unique_ptr<REPARSE_DATA_BUFFER, free_deleter<REPARSE_DATA_BUFFER
 }
 #endif
 
-GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec)
+GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec, bool resolve_relative)
 {
 #ifdef GHC_OS_WINDOWS
     path result;
@@ -2217,7 +2217,7 @@ GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec)
                     else {
                         result = substituteName;
                     }
-                    if (reparseData->SymbolicLinkReparseBuffer.Flags & 0x1 /*SYMLINK_FLAG_RELATIVE*/) {
+                    if (resolve_relative && reparseData->SymbolicLinkReparseBuffer.Flags & 0x1 /*SYMLINK_FLAG_RELATIVE*/) {
                         result = p.parent_path() / result;
                     }
                     break;
@@ -2233,6 +2233,7 @@ GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec)
     }
     return result;
 #else
+    (void)resolve_relative;
     size_t bufferSize = 256;
     while (true) {
         std::vector<char> buffer(bufferSize, static_cast<char>(0));
@@ -2250,6 +2251,11 @@ GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec)
 #endif
 }
 
+GHC_INLINE path resolveSymlink(const path& p, std::error_code& ec)
+{
+    return resolveSymlink(p, ec, true);
+}
+
 #ifdef GHC_OS_WINDOWS
 GHC_INLINE file_time_type timeFromFILETIME(const FILETIME& ft)
 {
@@ -4088,16 +4094,18 @@ GHC_INLINE void copy_symlink(const path& existing_symlink, const path& new_symli
 GHC_INLINE void copy_symlink(const path& existing_symlink, const path& new_symlink, std::error_code& ec) noexcept
 {
     ec.clear();
-    auto to = read_symlink(existing_symlink, ec);
+    auto resolved_to = read_symlink(existing_symlink, ec);
     if (!ec) {
 #ifdef GHC_OS_WINDOWS
-        auto resolved_to = to.is_absolute() ? to : existing_symlink.parent_path() / to;
-        auto to_directory = exists(resolved_to, ec) && is_directory(resolved_to, ec);
+        auto to = detail::resolveSymlink(existing_symlink, ec, false);
         if (!ec) {
-            detail::create_symlink_unchecked(to, new_symlink, to_directory, ec);
+            auto to_directory = exists(resolved_to, ec) && is_directory(resolved_to, ec);
+            if (!ec) {
+                detail::create_symlink_unchecked(to, new_symlink, to_directory, ec);
+            }
         }
 #else
-        create_symlink(to, new_symlink, ec);
+        create_symlink(resolved_to, new_symlink, ec);
 #endif
     }
 }
diff --git a/test/filesystem_test.cpp b/test/filesystem_test.cpp
index eb3ad37..0d1b940 100644
--- a/test/filesystem_test.cpp
+++ b/test/filesystem_test.cpp
@@ -1927,19 +1927,31 @@ TEST_CASE("fs.op.copy_symlink - copy_symlink", "[filesystem][operations][fs.op.c
 
         CHECK_NOTHROW(fs::copy_symlink("links/relative-dir-link", "links/relative-dir-copy"));
         CHECK(fs::is_directory("links/relative-dir-copy"));
+#ifdef GHC_OS_WINDOWS
+        CHECK(fs::read_symlink("links/relative-dir-copy") == fs::path("links/dir-target"));
+#else
         CHECK(fs::read_symlink("links/relative-dir-copy") == fs::path("dir-target"));
+#endif
 
         ec = std::make_error_code(std::errc::invalid_argument);
         CHECK_NOTHROW(fs::copy_symlink("links/relative-file-link", "links/relative-file-copy", ec));
         CHECK(!ec);
         CHECK(fs::is_regular_file("links/relative-file-copy"));
+#ifdef GHC_OS_WINDOWS
+        CHECK(fs::read_symlink("links/relative-file-copy") == fs::path("links/file-target"));
+#else
         CHECK(fs::read_symlink("links/relative-file-copy") == fs::path("file-target"));
+#endif
 
         fs::create_symlink("missing-target", "links/dangling-link");
         CHECK_NOTHROW(fs::copy_symlink("links/dangling-link", "links/dangling-copy", ec));
         CHECK(!ec);
         CHECK(fs::is_symlink("links/dangling-copy"));
+#ifdef GHC_OS_WINDOWS
+        CHECK(fs::read_symlink("links/dangling-copy") == fs::path("links/missing-target"));
+#else
         CHECK(fs::read_symlink("links/dangling-copy") == fs::path("missing-target"));
+#endif
 
         fs::create_symlink(fs::absolute("foo"), "links/absolute-link");
         CHECK_NOTHROW(fs::copy_symlink("links/absolute-link", "links/absolute-copy"));