[windows] Can't delete a closed file?

[Rumbu]

On Thursday, 9 May 2019 at 10:09:23 UTC, Cym13 wrote:
> Hi,
>
> this is likely not related to D itself but hopefully someone 
> can help me with this since I'm rather new to windows 
> programming, I mainly work on linux. I'm trying to bundle a DLL 
> in a binary, write it in a temp folder, use it and remove the 
> dangling file.
>
> So far I have the following file:
>
>     import std;
>
>     void main(string[] args) {
>         import core.runtime;
>         static immutable libcurl = import("libcurl.dll");
>
>         import std.file: write;
>         auto libpath = tempDir.buildPath("libcurl.dll");
>         libpath.write(libcurl);
>
>         auto libcurlMem = rt_loadLibrary(libpath.toStringz);
>
>         import std.net.curl;
>         "https://dlang.org/".byLine.count.writeln;
>
>         rt_unloadLibrary(libcurlMem);
>         remove(libpath);
>     }
>
> Compiled with:  dmd.exe -Jlibdir test.d
>
> It almost work, I can write, load and use the library, but when 
> it comes to
> removing it nothing works.
>
> std.file.FileException at std\file.d(1045): 
> C:\users\cym13\Temp\libcurl.dll: Access denied.
> ----------------
> 0x00402377 in EntryPoint
> 0x00413BC7 in EntryPoint
> 0x00413B49 in EntryPoint
> 0x004139E3 in EntryPoint
> 0x0040B77F in EntryPoint
> 0x7B4754C2 in call_process_entry
> 0x7B477FC6 in ExitProcess
> 0x7B4754CE in call_process_entry
>
> I tried using an explicit File handle to explicitely close the 
> file after
> writing to it but that doesn't change anything.
>
> I'm pretty sure I'm missing something basic about the way 
> windows handles
> open files but I don't know what, could someone explain why 
> this doesn't work
> the way I expect it to?

Since deploying a dll is a suspect behaviour outside a normal 
installation process, most probably you have a lock on the file 
put by windows defender or an antivirus if installed.

FreeLibrary doesn't guarantee that the dll file is closed, maybe 
other windows processes are accessing it (like prefetch).

Anyway, you are deploying a dll just to read a file, It's over 
engineering, use WinAPI UrlDownloadToFile instead or any other 
winapi functions.