On Windows QDir::mkpath and QFile::rename report success despite failing - c++

Question

I'm trying to add auto-update functionality to the app I'm working on. My solution works well on Linux, but I'm running into weird problems on Windows.
After unpacking the update package I'm trying to move it to the destination directory using the following function:
inline void recursiveMoveOrCopy(QDir source, QDir dest, bool move)
{
auto files = source.entryInfoList(QDir::Files);
auto dirs = source.entryInfoList(QDir::Dirs|QDir::NoDotAndDotDot);
// move / copy files
bool success = QDir{}.mkpath(dest.path());
if (!success){
throw std::runtime_error(qs("Could not crate directory %1")
.arg(dest.path()).toStdString());
}
qDebug()<<"created directory"<<dest.path();
dumpvar(QDir{}.exists(dest.path()));
for (auto& file: files){
QString sourcePath = file.filePath();
QString fileName = file.fileName();
QString destPath = dest.filePath(fileName);
QString backupPath = destPath + "_bck";
bool success;
bool backup = false;
if (QFile::exists(destPath))
backup = QFile::rename(destPath, backupPath);
ON_EXIT{
if (backup) {
QFile::remove(destPath);
QFile::rename(backupPath, destPath);
}
};
if (move) success = QFile::rename(sourcePath, destPath);
else success = QFile::copy(sourcePath, destPath);
qDebug()<<qs("move from %1 to %2 was %3").arg(sourcePath, destPath, success?"successful":"not sucessful");
if (success && backup){
QFile::remove(backupPath);
backup = false;
}
if (!success){
throw std::runtime_error(qs("Failed to %1 file %2 to %3")
.arg(move?"move":"copy")
.arg(sourcePath)
.arg(destPath)
.toStdString());
}
}
// recursively move/copy dirs
for (auto &dir: dirs) recursiveMoveOrCopy(dir.filePath(), dest.filePath(dir.fileName()), move);
}
I made a small package for testing with just 2 files and 1 directory:
$ tree .
.
├── katalog
│   └── plik
└── plik2
When I try to install this "update" the following is written to debug output by the move function:
"moving C:/Users/piotrek/AppData/Local/Temp/dres-update-image to C:/Program Files (x86)/DRES"
created directory "C:/Program Files (x86)/DRES"
QDir{}.exists(dest.path()) = true
"move from C:/Users/piotrek/AppData/Local/Temp/dres-update-image/plik2 to C:/Program Files (x86)/DRES/plik2 was successful"
created directory "C:/Program Files (x86)/DRES/katalog"
QDir{}.exists(dest.path()) = true
"move from C:/Users/piotrek/AppData/Local/Temp/dres-update-image/katalog/plik to C:/Program Files (x86)/DRES/katalog/plik was successful"
As in: every single operation succeeded. But when I look into the target directory, the directory katalog doesn't exist (the file plik2 does however).
Note that even though the directory does NOT exist, QDir::exists reports that it does.
It's not a permission problem, when I was testing this I modified C:/Program Files (x86)/DRES to give Everyone full access.
Please tell me I'm not crazy. What the hell is going on here?
EDIT: Thanks to Rudolfs' suggestion to use Process Monitor I discovered the the files are actually being written to C:\Users\piotrek\AppData\Local\VirtualStore\Program Files (x86)\DRES. What exactly is going on here and how do I fix this?

Answer 1

Ok, I figured it out.
I had to use the following code to disable VirtualStore virtualization for the whole app:
#ifdef Q_OS_WIN32
#include <windows.h>
QString getWinError()
{
DWORD dw = GetLastError();
LPWSTR lpMsgBuf = NULL;
FormatMessageW(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dw,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPWSTR) &lpMsgBuf,
0, NULL );
QString str = QString::fromWCharArray(lpMsgBuf);
LocalFree(lpMsgBuf);
return str;
}
bool disableVirtualStore()
{
HANDLE token;
DWORD tokenInformation = 0;
if(!OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &token)){
qWarning()<<getWinError();
return FALSE;
}
ON_EXIT{
CloseHandle(token);
};
if(!SetTokenInformation(token, TokenVirtualizationEnabled,
&tokenInformation, sizeof(tokenInformation))) {
qWarning()<<getWinError();
return FALSE;
}
return TRUE;
}
#endif
Now I can normally write to all folders that I have write access to, and since Windows no longer lies to me about having write access, I can start an elevated helper app to move files to folders where I don't have write permission.