[Support] Add sys::fs::set_current_path() (aka chdir)

[labath]

Summary

This adds a cross-platform way of setting the current working directory
analogous to the existing current_path() function used for retrieving
it. The function will be used in lldb.

[aaron.ballman]

Windows code looks fine to me.

[silvas]

We have a chdir in lib/Basic/VirtualFileSystem.cpp that probably can be moved to using this API in a followup patch.

[silvas]

In D29035#654536, @silvas wrote:

We have a chdir in lib/Basic/VirtualFileSystem.cpp that probably can be moved to using this API in a followup patch.

that is clang/lib/Basic/VirtualFileSystem.cpp

[labath]

Thanks for the review. Main two usages for chdir are:

• launching the debugged process in a given directory
• we have a remote stub, which (besides doing remote debugging) can execute user-supplied shell commands on the target device. These commands need a CWD.

I'll create a follow-up clang patch after this.

include/llvm/Support/FileSystem.h

 
 /// @brief Get the current path.
 ///
 /// @param result Holds the current path on return.
 /// @returns errc::success if the current path has been stored in result,
 ///          otherwise a platform-specific error_code.
 std::error_code current_path(SmallVectorImpl<char> &result);
 
+/// @brief Set the current path.
+///
+/// @param path The path to set.
+/// @returns errc::success if the current path was successfully set,
+///          otherwise a platform-specific error_code.
+std::error_code set_current_path(const Twine &path);
+
 /// @brief Remove path. Equivalent to POSIX remove().
 ///
 /// @param path Input path.
 /// @returns errc::success if path has been removed or didn't exist, otherwise a
 ///          platform-specific error code. If IgnoreNonExisting is false, also
 ///          returns error if the file didn't exist.
 std::error_code remove(const Twine &path, bool IgnoreNonExisting = true);
 

lib/Support/Unix/Path.inc

while (true) {
     } else
       break;
   }
 
   result.set_size(strlen(result.data()));
   return std::error_code();
 }
 
+std::error_code set_current_path(const Twine &path) {
+  SmallString<128> path_storage;
+  StringRef p = path.toNullTerminatedStringRef(path_storage);
+
+  if (::chdir(p.begin()) == -1)
+    return std::error_code(errno, std::generic_category());
+
+  return std::error_code();
+}
+
 std::error_code create_directory(const Twine &path, bool IgnoreExisting,
                                  perms Perms) {
   SmallString<128> path_storage;
   StringRef p = path.toNullTerminatedStringRef(path_storage);
 
   if (::mkdir(p.begin(), Perms) == -1) {
     if (errno != EEXIST || !IgnoreExisting)
       return std::error_code(errno, std::generic_category());

lib/Support/Windows/Path.inc

std::error_code current_path(SmallVectorImpl<char> &result) {
   } while (len > cur_path.capacity());
 
   // On success, GetCurrentDirectoryW returns the number of characters not
   // including the null-terminator.
   cur_path.set_size(len);
   return UTF16ToUTF8(cur_path.begin(), cur_path.size(), result);
 }
 
+std::error_code set_current_path(const Twine &path) {
+  // Convert to utf-16.
+  SmallVector<wchar_t, 128> wide_path;
+  if (std::error_code ec = widenPath(path, wide_path))
+    return ec;
+
+  if (!::SetCurrentDirectoryW(wide_path.begin()))
+    return mapWindowsError(::GetLastError());
+
+  return std::error_code();
+}
+
 std::error_code create_directory(const Twine &path, bool IgnoreExisting,
                                  perms Perms) {
   SmallVector<wchar_t, 128> path_utf16;
 
   if (std::error_code ec = widenPath(path, path_utf16))
     return ec;
 
   if (!::CreateDirectoryW(path_utf16.begin(), NULL)) {

unittests/Support/Path.cpp

if (!ResultPath.empty()) {
     fs::UniqueID D1, D2;
     ASSERT_NO_ERROR(fs::getUniqueID(Twine(TempPath), D1));
     ASSERT_NO_ERROR(fs::getUniqueID(Twine(ResultPath), D2));
     ASSERT_EQ(D1, D2);
   }
 
   ::close(FileDescriptor);
 }
+
+TEST_F(FileSystemTest, set_current_path) {
+  SmallString<128> path;
+
+  ASSERT_NO_ERROR(fs::current_path(path));
+  ASSERT_NE(TestDirectory, path);
+
+  struct RestorePath {
+    SmallString<128> path;
+    RestorePath(const SmallString<128> &path) : path(path) {}
+    ~RestorePath() { fs::set_current_path(path); }
+  } restore_path(path);
+
+  ASSERT_NO_ERROR(fs::set_current_path(TestDirectory));
+
+  ASSERT_NO_ERROR(fs::current_path(path));
+  ASSERT_EQ(TestDirectory, path);
+}
+
 } // anonymous namespace