Why is my 64 bit service running as 32 bit?

Question

I have a Windows Service that I'm having this issue with.

• In Visual Studio I've set its Platform Target to 64 bit
• I've run CorFlags to verify that it is set correctly, I get this:

Version   : v4.0.30319
CLR Header: 2.5  
PE        : PE32+
CorFlags  : 0x1    
ILONLY    : 1       
32BITREQ  : 0        
32BITPREF : 0        
Signed    : 0

I even tried running Corflags with the 32BITREQ- and 32BITPREF- flags to make sure it was set to what it's supposed to be but no dice. In the taskManager it shows up as:

MyServiceName (32 bit)

Service was installed with Topshelf 3.0 and is running on Windows Server 2012 R2 Standard. What's going on here?

Answer 1

Maybe your installation tool is using 32 bit installutil to install the process? As I understand from this article

using 32 bit installutil results in forcing the executable to run as 32 bit in a 64 bit OS.

This part of the article in particular seems to say so:

To get around this problem, please run installutil.exe outside of the appropriate Framework/Framework64 directory. If you have a snap-in built for ILONLY (ILONLY indicates that the executable contains pure IL code and can run either as 32-bit or as a 64-bit process), but want to register it under the wow64 hive, use installutil.exe that is available in the directory %windir%\microsoft.net\framework\v2.n.n.n. For the 64-bit hive registration, run installutil.exe from the directory %windir%\microsoft.net\framework64\v2.n.n.n.

Answer 2

I had this issue when a previous version of the service had been 32 bit. I knew the currently installed one wasn't (checked CORFLAGS), but the process associated with the service was being created as 32 bit anyway, and for the life of me I couldn't work out why.

After a reboot the problem went away. I wonder if the Service Control Manager 'remembers' the bitness for each service, as a startup optimization (or something).