CODEWITHSUNDEEP
c++ccreatefile
tsc_chazz
tsc_chazz

Reputation: 206

Windows 8: CreateFile() returns INVALID_HANDLE_VALUE, immediate GetLastError shows 0

I am opening a file with CreateFile on Windows 8 from within a printer filter environment. The code is effectively straight C, even though the filter is built in C++. CreateFile returns INVALID_HANDLE_VALUE but an immediate call to GetLastError returns 0. I have seen this before, back in the old NT4 days (and through to Windows 7) if a directory of the same name as the file existed, a file open attempt would fail with error 0; but I have checked and the file name is different from any subdirectories in the destination directory.

Code:

io_buf[fh].fh = CreateFile(name, GENERIC_READ|GENERIC_WRITE, 0, p_sa,
                           CREATE_ALWAYS, 0, (HANDLE)0);
io_buf[fh].read_mode = FALSE;
io_buf[fh].file_start = 0L;
io_buf[fh].folder = 0;

if (io_buf[fh].fh == INVALID_HANDLE_VALUE)
{
    LogMsg("BufCreate: CreateFile failed (%ld); retrying with SharedWrite\r\n", GetLastError());
    io_buf[fh].fh = CreateFile(name, GENERIC_READ|GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, p_sa,
                               CREATE_ALWAYS, 0, (HANDLE) 0);
}
if (io_buf[fh].fh == INVALID_HANDLE_VALUE)
{
    LogMsg("BufCreate: CreateFile failed (%ld)\r\n", GetLastError());
    return (Vers_FAILURE);
}

LogMsg output:

Render 15:41:46.715: BufCreate: CreateFile failed (0); retrying with SharedWrite

Render 15:41:46.715: BufCreate: CreateFile failed (0)

Because this occurs relatively randomly, sending it to MS would not work; they'd fire it back to me with a "no rep" and I'd get dinged for the SRX. Has anyone got any clue on how I would proceed?

Upvotes: 0

Views: 846

Answers (1)

tsc_chazz
tsc_chazz

Reputation: 206

This is vexing. Turns out that I was not writing the file where I thought I was, and that's why it failed. But it should have returned error 5 (Access denied), and I was led up a stump because of this bedamned 0 in GetLastError.

For what it's worth: I had created a path to a temp directory. Because my security context at the time was LocalSystem (I'm in the PrinterPipeline service), that file was in c:\Windows\System32\Services\LocalService\AppData\Local\Temp. No ordinary user can reach that space, and the attempt will quite possibly leave your OS hooped. I had changed to user security context to write to C:\Temp, and was getting a failure because I had forgotten to change my filename to C:\Temp. The error 0 made it look like possibly I was faced with file system redirection mapping c:\temp into LocalService space.

Correcting that so that I was actually writing where I thought I was got rid of the failure... but I still don't understand why Windows was handing me back an error 0.

Upvotes: 1

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