What were the rules on x64 exe and x32 dll?

  • Thread starter Thread starter Norman Diamond
  • Start date Start date
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Norman Diamond

Part of this message should not be surprising, but part of it is.

In Visual Studio 2008 plus recently released SDK, I compiled a C# program
for x64, including calls to functions in a C++ DLL. I forgot that the DLL
was 32-bit only.

Running the debug version under control of Visual Studio 2008, the program
started running. It did its C# initializations, called functions in the C++
DLL, did more C# initializations, and displayed its main form. It continued
running until I stupidly told it to call some DotNet methods to open an
OleDb connection to an Excel file. Microsoft's efforts to get vendors to
support x64 didn't include Microsoft as a vendor. OK, that's a separate
issue, and we're getting ahead of ourselves here. Nonetheless, *how* did we
get ahead of ourselves here?

Running the release version by double-clicking in Windows Explorer, the
program started but didn't get very far. It did its C# initializations,
tried to call its first function in the C++ DLL, and crashed long before it
would be ready to display a form.

Task Manager says that both the vsshost version and the standalone version
are running as native x64 executables, not as *32 wows.

How did the debug version get to call that 32-bit DLL and not crash?
 
OK, solved, more or less. The call crashed. The Visual Studio 2008
debugger prevents debugging of the Form Load handler, displaying the form as
if everything worked perfectly.
 
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