I have an application which has many services and one UI module. All these are developed in VC++ 6.0. The total KLOC would be 560 KLOC.
It uses Mutltithreading,MFC and all datatypes like word,int, long.
Now we need to support 64bit OS. What would be the changes we would need to make to the product.
By support i mean both like running the application on a 64bit OS and also making use of the 64bit memory.
Edit: I am ruling out migration to VS2005 or anything higher than VC6.0 due to time constraints.
So what changes need to be done.
64bit Windows includes 32bit via WOW. Any 32bit application should just continue to work.
(It is only drivers that have to match the bitness of the OS.)
[Note to commenters: plugins—of whatever type—are not separate applications but dlls used by other applications which do need to match the host. In that case you also get the same problem where 64bit extensions are incompatible with 32bit hosts.]
As Richard says, the 32-bit version should continue to work unless you've got a driver or a shell extension or something.
However if you do need to upgrade the code you're going to have to upgrade the compiler too: I don't think MFC got good 64-bit support until VS2005 or later. I'd suggest you get the 32-bit code building in VS2010 - this will not be trivial - and then start thinking about converting it to 64-bit. You can of course leave the production 32-bit builds in VC6 but then you add maintainership burden.
You'll probably get most of the way converting by flipping the compiler to 64-bit and turning on full warnings - particularly given the size of your code it may be impractical to review it all. One thing to watch out for is storing pointers in ints, dwords, etc. which may now be too short to hold the pointer - you need DWORD_PTR etc. now - but I think the warnings do catch that.
Or if this is in many components then you might get away with only migrating a few components to 64-bit. Then, unfortunately, you've got data length issues for communication between the two versions.
You must convert to a newer compiler. Time constraints are pretty much irrelevant. The VC6 compiler simply cannot generate 64 bits code. Every pointer it generates is 32 bits, for starters. If you need to access "64 bit memory", i.e. memory above 0x00000000FFFFFFFF, then 32 bits is simply not enough.
If you're ruling out changing your IDE to one that intrinsically supports 64-bit compiling and debugging, you're making your job unnecessarily more complex. Are you sure it's not worth the hit?
Just for running on a 64bit OS, you won't need to make any changes. That's what WOW64 is for.
If, however, you want to run 64bit natively (i.e., access the 64bit memory space) you will have to compile as 64bit. That means using an IDE that supports 64bit. There is no way around this.
Most programs should have no problem converting to 64bit if they are written with decent coding standards (mainly, no assumptions about the size of a pointer, like int-pointer conversions). You'll get a lot of warnings about things like std::size_t conversions, but they will be fairly meaningless.
Related
I'm not a hardware guy, but I know that Visual Studio in a 64 bit version issue request was declined by Microsoft stating that a 64 bit version would not have good performance.
Two noticeable differences between the two that I feel are obvious is the code base. One began it's life in 1997, one would think that means more baggage on the Visual Studio side, less opportunities to have very modern application architecture and code and that may make it harder and possibly stuff may be built to perform on 32 bit and for some reason is not suitable for 64 bit? I don't know.
Visual Studio Code on the other hand is an modern Electron app which means it pretty much just compiled HTML. CSS and JavaScript. I'm betting making a version of Visual Studio Code has little in the way of obstructions and although performance may not be something truly noticeable, why not?
P.S.
I still would like to understand what areas may be improved in performance and if that improvement is negligible to the a developer. Any additional info or fun facts you may know would be great I would like to have as much info as possible and I will update the question with any hard facts I uncover that are not mentioned.
The existence of 64-bit Visual Studio Code is largely a side-effect of the fact that the Node.js- and Chromium-based runtimes of Electron support both 32- and 64-bit architectures, not a primary design goal for the application. Microsoft developed VS Code with Electron, a framework used to build desktop applications with web technologies.
Because Electron already includes runtimes for both architectures (and for different operating systems), VS Code can provide both versions with little additional effort—Electron abstracts the differences between machines from the JavaScript code.
By contrast, Microsoft distributes much of Visual Studio as compiled binaries that contain machine-specific instructions, and the cost of rewriting and maintaining the source code for 64-bits historically outweighed any benefits. In general, a 64-bit program isn't noticeably faster to the end user than its 32-bit counterpart if it never exceeds the limitations of a 32-bit system. Visual Studio's IDE shell doesn't do much heavy-lifting—the bulk of the expensive processing in a typical workflow is performed by the integrated toolchains (compilers, etc.) which usually support 64-bit systems.
With this in mind, any benefits we may notice from running a 64-bit version of VS Code are similar to those we would see from using a 64-bit web browser. Most significantly, a 64-bit version can address more than 4 GB of memory, which may matter if we need to open a lot of files simultaneously or very large files, or if we use many heavy extensions. So—most important to us developers—the editor won't run out of memory when abused.
While this sounds like an insurance policy worth signing, even if we never hit those memory limits, remember that 64-bit applications generally consume more memory than their 32-bit counterparts. We may want to choose the 32-bit version if we desire a smaller memory footprint. Most developers may never hit that 4 GB wall.
In rare cases, we may need to choose either a 32-bit or 64-bit version if we use an extension that wraps native code like a DLL built for a specific architecture.
Any other consequences, positive or negative, that we experience from using a 64-bit version of VSCode depend on the versions of Electron's underlying runtime components and the operating system they run on. These characteristics change continuously as development progresses. For this reason, it's difficult to state in a general manner that the 32-bit or 64-bit versions outperform the other.
For example, the V8 JavaScript engine historically disabled some optimizations on 64-bit systems that are enabled today. Certain optimizations are only available when the operating system provides facilities for them.
Future 64-bit versions on Windows may take advantage of address space layout randomization for improved security (more bits in the address space increases entropy).
For most users, these nuances really don't matter. Choose a version that matches the architecture of your system, and reserve switching only if you encounter problems. Updates to the editor will continue to bring optimizations for its underlying components. If resource usage is big concern, you may not want to use a GUI editor in the first place.
I haven't worked much on windows but have interacted with x86, x64 and ARM (Both 32-bit and 64-bit instruction set size) processors. Based on my experience, before writing the code in 64-bit format we thought: Do we really need 64-bit size instructions? If our operation can be performed within 32 bits, then why shall we need another 32 bits?
Think of it like this: You have a processor with 64-bit address and 64-bit data buses and 64-bit size registers. Almost all of the instructions of your program requires maximum 32 bits. What will you do? Well, I think there are two ways now:
Create a 64-bit version of your program and run all the 32-bit instructions on your 64-bit processor. (Wasting 32-bits or your processor in each instruction cycle, and filling the Program Counter with an address which is 4 bytes ahead). Your application / program which could have been executed in 256 MB of RAM now requires 512 MB, due to which other programs or processes running on the RAM will suffer.
Keep the program format to 32-bit and combine 2 32-bit instructions to be pushed into your 64-bit processor for execution.
Obviously, second approach will run faster with the same resources.
But yes, if your program is containing more instructions which are really 64-bit in size; For eg. Processing 4K videos (Better on 64-bit processor with 64-bit instruction set) or performing floating-points operations with up to 15 decimal digit precision, etc. Then, it is better to create 64-bit program file.
Long story in short: Try to write compact software and leverage the hardware as much as possible.
So far, what I have read Here, Here and Here; I came to know that most of the components of VS require only 32-bits instruction size.
Hope it explains.
Thanks
4 years later, in 2021, you now have:
"Microsoft's Visual Studio 2022 is moving to 64-bit" from Mary Jo Foley
It references the official publication "Visual Studio 2022" from Amanda Silver, CVP of Product, Developer Division
Visual Studio 2022 is 64-bit
Visual Studio 2022 will be a 64-bit application, no longer limited to ~4gb of memory in the main devenv.exe process. With a 64-bit Visual Studio on Windows, you can open, edit, run, and debug even the biggest and most complex solutions without running out of memory.
While Visual Studio is going 64-bit, this doesn’t change the types or bitness of the applications you build with Visual Studio. Visual Studio will continue to be a great tool for building 32-bit apps.
I find it really satisfying to watch this video of Visual Studio scaling up to use the additional memory that’s available to a 64-bit process as it opens a solution with 1,600 projects and ~300k files.
Here’s to no more out-of-memory exceptions. 🎉
I was recently fixing some IAT on MoleBox packed executable and saw that it links with kernel32 functions: '_lopen', '_lwrite' and '_lread'. This site states that those API's are provided for compatibility with 16-bit versions of Windows. I undesrtand that 'Win16' applications can't be executed in long mode (yes - I'm running Win8.1 x64) - so what is the purpose those to be still included in 'kernel32.dll'?
By the way those functions aren't even included in the 'msdn' library.
EDIT: It also seems that those function aren't actually 16-bit! They're taking 32-bit parameters on the stack.
It's not that the functions can be called by 16 bit applications. Clearly they cannot because they live in 32 bit and 64 bit modules. The point is (was) to make it easier for developers to compile old programs without having to re-write them.
Now, in 2015 there's no real need to cater for developers that have 16 bit programs that they wish to re-compile. That is probably not happening any more to any significant level. But if you roll back the clock 20 years then this was a real concern. And hence MS included these compat crutches. And once they had been included, then MS probably decided to leave them there so as not to break binary compatibility. MS does go to great lengths to avoid breaking old programs. Were these functions to be removed, any programs that rely on them would break.
Microsoft doesn't remove functions "just because" they're old. They will remove these functions as soon as they would require a reimplementation, but for now it takes less work to keep them.
I realize that there will likely be no special converter programs or anything easy like that for such a task, but it imperative that I find some way to get a 16-bit program to run in 64-bit Windows. Due to the large amount of resources that must be dedicated to them, emulators will not be a good solution.
The idea I had for this project was to decompile all the code from a 16-bit program, copy it, and re-compile it into 64-bit code. Is this at all possible using Eclipse or another programming environment?
Basically, I want to make a 16-bit program run in 64-bit Windows without emulators. I realize that it's a tall order, but is it conceivable?
The problem goes beyond translating 16-bit instructions with 64-bit instructions. There is also the ABI (Application Binary Interface) used by the program to communicate with the rest of the system. A 16-bit program likely uses a lot of DOS calls and it's not unlikely it tries to access hardware directly too. There is no way this can be translated automatically. Even if such a solution existed, I highly doubt the result would be more efficient than running in a virtual machine (which actually is very efficient). Further more, programs written for 16-bit environment are often not very scalable, and completely unable to handle amounts of data beyond the capacities of the original target platform.
So I'd say there are really just two realistic solutions: Run it in a virtual machine. Or if that doesn't cut it, write a new application from scratch that does the same thing.
Even if this is a very old question, but I thought I'd write this solution for anyone still looking out there:
Using something like winevdm -which is a very light windows program- you can run 16-bit Windows (Windows 1.x, 2.x, 3.0, 3.1, etc.) on 64-bit Windows apps very easily!
I am interested whether I can write an application which will be able to call some code without emulation layer and some code inside of 32 bit emulation layer.
The main reason for that is that I will need to use API SetWindowHook and I want to set hook both for 64 bit and 32 bit applications.
Sure, I can create 2 application (one for 32 bit and another for 64 bit) and launch them simultaneously. However, I will need more code to manage them (start, stop, upgrade and etc).
So, I am looking whether it's possible at all to have one application.
The only idea which I have is to have one application and 2 COM DLL's (32bit and 64bit) and use a surrogate process to run code of 32 bit. However, it will require some additional COM wrappers and so on.
I cannot suggest a better way of doing it but what I can do is give you the source to a simple hook-based tool which does exactly the same kind of thing. Feel free to the bits that are useful to you:
http://www.pretentiousname.com/NoBarTab/NoBarTab_poc3.zip
(If this URL breaks in the future, just go up a level; it'd probably because I've finished it and put a real page up for the tool and its source.)
It's a VS2010 C++ project but should be easy to compile in older IDEs. (Writing this actually put me off using VS2010 any further for now, heh.)
Obviously, if you use it, please rename any window classes and binary names to avoid conflicts with my tool. (Anything with "NoBarTab" in the name.)
FWIW, this is a tool I started writing a few weeks ago but haven't got around to finishing. The hooking part is finished, though. It hooks window creation so that it can, for specific processes, remove tabs from the Windows 7 taskbar. (I hate the way that feature is used by VMware, in particular.) I was going to release the source code anyway when I finished it...
The 32/64-bit hooking part is all done. The only thing I haven't got around to is adding a config UI so you can specify which processes it should care about, but that's not important for what you are doing.
(I should say that the way I remove tabs from the Win7 taskbar is a complete hack and might break with future versions of Windows. There's no documented way to do that so I had to settle on a nasty kludge. The actual hooking code that you'd be interested in is all "proper", though.)
Also, I made it so that almost all of the real logic is within the main 64-bit exe. The 32-bit EXE just exists to install the 32-bit hook DLL and both the 32-bit and 64-bit hook DLLs just post a message to the main 64-bit exe's hidden window. Whether that is suitable for what you're doing I leave to you to decide, but I figure it probably fits with your desire to have everything in one place as much as possible.
Hope it's useful!
SetWinEventHook is a higher-level hooking API which handles the 32-bit/64-bit stuff for you. This came up in the answers to another question today and I thought it'd be worth mentioning here in case that solved your problem. Full credit to #atzz for his answer over there.
Whether or not SetWinEventHook is as suitable to you as the lower-level SetWindowsHookEx will depend on exactly what you're doing. (In my case, I could probably re-write the NoBarTab code in my other answer to use the more simple API. Haven't looked in detail yet, though.)
The biggest reason for the emulation layer is that your 64-bit code is going to have a larger address space. Say, for example, you have data addressed at 0x12345678aa000000. If you pass that pointer straight to 32-bit code, it will get truncated to 32-bit address space. That is, to say, that the high-order 32 bits get removed. So the address to your data looks like 0x00000000aa000000 to your 32-bit code. This is clearly a completely different area and not what you intended.
Yes, it's possible. No you shouldn't do it unless you're extremely experience with x86 and x64 assembly, and have access to the 32-bit source code to ensure that it knows that its actually running in 64-bit space and also have access to 64-bit code to ensure that all of the data it passes to the 32-bit code is only in the 32-bit address range.
No, executing 32-bit code without the emulation layer is undesirable unless you are trying to make an UBER UGLY hack.
I think your only hope is to do it through something like out-of-process COM because each process has to be all 32 bit or all 64 bit.
Perhaps I'm missing a major point of the x64 platform here, but my perception was that x64 applications were only better performing than x86 versions (on an x64 OS and hardware, obviously) when large amounts of memory, large pointers, or other demanding factors were involved.
However, I've started to notice some smaller applications offering x64 versions of their installers in addition to the standard x86 versions. Since x86 runs just fine on Windows x64 using WoW, is there any benefit to me releasing an x64-compiled version of my application? As I see it:
Pros:
Potentially higher performance (in what conditions, though)
Cons:
Additional build to create/support
Potential bugs in x64 target that aren't present in the x86 target
Dependence on x64 versions of vendor/OS DLLs, requiring different install checklist and introducing additional troubleshooting complications
What are some compelling reasons that should cause me to reconsider adding an x64-compiled version of my app?
Another potential reason for compiling and debugging an x64 version is that it may expose hidden bugs in the x86 version. For example, this may expose improper conversions between 32-bit integers and (now) 64-bit pointers. This also positions you to support x64 in the future.
However, unless your application would benefit from 64-bit integers, additional cpu registers, a larger memory space (beyond 3.5Gb), or implement a device driver, staying with 32-bit application is fine. All major operating systems support running both x32 and x64 applications at the same time so there will not be a major push towards 64-bit only applications.
BTW. Applications based on .NET automatically benefit from being executed on a 64-bit system without any code changes. No additional testing required.
Potential performance improvement relates mostly to usage of 64-bit integers (around 4 times as fast in an x64 build on my machine than in x86 on the same) and the fact that compilers may assume some CPU features to be universally present in CPUs supporting x64, such as SSE2, &c.; this can lead to more optimized code.
For many applications, especially small ones it isn't too difficult to be 64-bit clean, for larger ones it's a major headache, granted. Compelling reasons are few, usually. But some platforms don't install their 32-bit support in 64-bit versions by default (I think FreeBSD needs to be explicitly told to do so, but I may err on that).
Your program will benefit if it uses a lot of long longs and WOW does of course mean a minor performance hit(very minor though because the CPU has a compatibility mode for such this reason)...
Windows support for 32 bit programs will be degrading in the future(albeit slowly) so I say in another year or 2, you can just about wonder why you would want to deploy a 32 bit application...
Also, a 64 bit build of your application, can actually be much more optimized than a 32 bit build because with 64 bit, you are guaranteed to have quite a few things, such as SSE2.
Performance; x86_64 is faster than x86 by a small amount (that also depends on your compiler), for the reasons already stated. Also, it's easier to support really huge data sets, but of course many applications never need go there.
Certainly on Linux and OS X, you really should support x86_64; I'm typing this to a 64 bit browser on OS X, and my Linux box in the corner is also 64 bit almost exclusively. 64 bit Windows is a bit more of a question, but that is now coming (with the drivers).
This is often based on human factors rather than objective technical reasoning. 64-bit is the latest and greatest and must be better than 32-bit. If customers want it the customer is always right. Have spoke with windows users saying their goal was to make it such that when they view their process list in windows *32 does not appear next to any of their apps.
Often times this is also fueled by confusion on the point of compatibility where people have 64-bit operating systems and just want to make sure the software will work on their computers. Expecting average people to understand the technical demarcation line between 32-bit processes on a 64-bit OS is unrealistic. Unless explicitly stated on the packaging it can be a point of confusion/concern for a customer purchasing new software. Often times you will see 64-bit mentioned for this reason. Typically this really means only 64-bit compatibility.
Now there are a few 64-bit applications (flash player and google earth top my list) that can't come soon enough.
Here's one reason: integrating with 64-bit apps, like writing a shell extension. A 64-bit process cannot load a 32-bit DLL directly, so you have to make yours 64-bit as well.
One factor that hasn't been mentioned yet: WoW64 Is Now an Optional Feature for Server Core. Only an issue if your application needs to run on server systems, of course.
Similarly, Windows PE, Windows RE, etc., do not include Wow64.