[libcxx] Implement the current_path function for windows

Differential Revision: https://reviews.llvm.org/D91169

1 files changed, 21 insertions, 4 deletions

diff --git a/libcxx/src/filesystem/operations.cpp b/libcxx/src/filesystem/operations.cpp
index fcb5c2d..429a585 100644
--- a/libcxx/src/filesystem/operations.cpp
+++ b/libcxx/src/filesystem/operations.cpp
@@ -1022,15 +1022,32 @@ void __create_symlink(path const& from, path const& to, error_code* ec) {
 path __current_path(error_code* ec) {
   ErrorHandler<path> err("current_path", ec);
 
+#if defined(_LIBCPP_WIN32API)
+  // Common extension outside of POSIX getcwd() spec, without needing to
+  // preallocate a buffer. Also supported by a number of other POSIX libcs.
+  int size = 0;
+  path::value_type* ptr = nullptr;
+  typedef decltype(&::free) Deleter;
+  Deleter deleter = &::free;
+#else
   auto size = ::pathconf(".", _PC_PATH_MAX);
   _LIBCPP_ASSERT(size >= 0, "pathconf returned a 0 as max size");
 
-  auto buff = unique_ptr<char[]>(new char[size + 1]);
-  char* ret;
-  if ((ret = ::getcwd(buff.get(), static_cast<size_t>(size))) == nullptr)
+  auto buff = unique_ptr<path::value_type[]>(new path::value_type[size + 1]);
+  path::value_type* ptr = buff.get();
+
+  // Preallocated buffer, don't free the buffer in the second unique_ptr
+  // below.
+  struct Deleter { void operator()(void*) const {} };
+  Deleter deleter;
+#endif
+
+  unique_ptr<path::value_type, Deleter> hold(detail::getcwd(ptr, size),
+                                             deleter);
+  if (hold.get() == nullptr)
     return err.report(capture_errno(), "call to getcwd failed");
 
-  return {buff.get()};
+  return {hold.get()};
 }
 
 void __current_path(const path& p, error_code* ec) {