Is it wrong to pinvoke user32.dll on 64 bit Windows, from a 64 bit app? I've done this successfully a number of times and never had an error, but it seems contradictory. Should I look for user64.dll instead?
+11
A:
The name user32.dll is misleading. It's the 64 bit version of user32.dll you're calling. The 64 bit version is located at %windir%\System32\user32.dll.
A 32-bit version is included for compatibility with 32-bit applications. It's located at %windir%\SysWOW64\user32.dll. You can inspect them using the dumpbin utility:
System32\user32.dll:
FILE HEADER VALUES
8664 machine (x64)
SysWOW64\user32.dll:
FILE HEADER VALUES
14C machine (x86)
Mehrdad Afshari
2009-10-08 22:01:36
It is misleading now, but it was originally named such to differentiate between 16 and 32 bit wasn't it? But they can hardly change the name, that'd break too many things...
Matthew Scharley
2009-10-08 22:04:31
Yeah. I distinctly remember general protection faults caused by "USER.EXE" in Windows 3.1 in my childhood days.
Mehrdad Afshari
2009-10-08 22:14:33
Gotta love how the System32 directory is still called that in 64 bit windows :-)
Kragen
2009-10-08 22:43:49
A:
There is no user64.dll for the exact same reason you just describe, .net program can be agnostic to cpu architecture so the same code needs to work on x86 and x64.
If you take your program to x86 platform it will still run without any modifications.
I guess that when they named user32.dll they didn't have those scenarios in mind.
Shay Erlichmen
2009-10-08 22:06:04