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c++visual-studio64-bit32bit-64bitmapserver

Cannot see variables when debugging a x64 bit DLL in Visual Studio

I am trying to step through a C/C++ program (MapServer) in Visual Studio, but I cannot see the local variables.

I created a new project by adding the main .exe I built from source. I can set break points and step through the program without problem, but I cannot see what is stored in any of the variables. I am running all this on a Virtual Machine - the host OS is Windows 10, and the VM is Windows 7.

The program is:

  • built as a debug release
  • has no optimizations
  • the symbols load fine

I am fairly certain it is due to it being a x64 bit release, as I can use the exact same approach for a x32 build and see the variables.

Example of the x32 debugger (the first 5 variables are correct - the others are unset):

Working debug session

Example of x64 debug session (note the program works fine):

Failing session

I thought it may be due to VS2008, so I also tried in VS2015, but had similar (failing) results:

enter image description here

Trying to access variables in the Immediate Window produces:

// working VS2008 x32 build
map->name
0x00ffcb40 "WFS_server"

// VS2008 x64 build
map->name
0x0000000000000000 <Bad Ptr>

// VS2015 x64 build
map->name  
0x0000000000000000 <NULL>

Am I missing some debugger setting in Visual Studio to set the debug project to x64? Or is there some casting issue in the source code that produces this?

Any pointers appreciated..

Solution

  • The above was caused by stdrup being deprecated on Windows, and the heap becoming corrupted.

    The MapServer issue on GitHub can be seen at https://github.com/mapserver/mapserver/pull/5277

    This question also describes a similar issue: Heap corruption with strdup