Debugging a user's crash from assembly

I've got a software application which some users report reliably crashes in certain situations. I can't reproduce it on any of the machines I've got so I'm feeling pretty stuck as to how to solve it.

A user posted me the assembly line where the crash happens, like this:

00505e58 1000 adc [eax],al
00505e5a cc int 3
00505e5b cc int 3
00505e5c cc int 3
00505e5d cc int 3
00505e5e cc int 3
00505e5f cc int 3
00505e60 55 push ebp
00505e61 8bec mov ebp,esp
00505e63 83ec1c sub esp,0x1c
FAULT -> 00505e66 ff4f08 dec dword ptr [edi+0x8] ds:0023:00000008=????????
00505e69 53 push ebx
00505e6a 56 push esi
00505e6b 0f85b00开发者_高级运维00000 jne Construct2+0x105f21 (00505f21)
00505e71 8d9894010000 lea ebx,[eax+0x194]
00505e77 8d45f0 lea eax,[ebp-0x10]
00505e7a 8bcb mov ecx,ebx
00505e7c e8ef4ff1ff call Construct2+0x1ae70 (0041ae70)
00505e81 8d45e4 lea eax,[ebp-0x1c]
00505e84 8bcb mov ecx,ebx
00505e86 e88580fdff call Construct2+0xddf10 (004ddf10)

I'm using Visual Studio 2010 and have my .pdbs for the build I gave the user. Is it possible to turn this assembly trace in to the faulting code line?

If you could get a full crash dump of your app when it crashes, then you could bring up the dmp in either windbg or Visual Studio and debug with source code rather easily. There's plenty of info on the web for getting a dump and debugging. For example, if you have a dump and matching pdb and bring thsi up in windbg, you can just do a ".lines" and see exactly where this is happening.

If you don't have a dump, then one way to do this is to run your app locally and look at the code at this address. It looks like your app, which I'm assuming is Construct2.exe, starts off at a base address of 0x0040000 and you're crashing at 0x00505E66 where EDI is 0. So if you flip to diassembly view, go to this address (or set a bp) then look at the source and you're good to go.