Database Users

decomiling and recompiling - newb question

Hi,
Can someone assist me with how i might go about decompiling or viewing a dll, making changes to it and recompiling it? What tools can i use to do this?
I have tried copying some of the dlls from my device over to my local pc, however most of the time i get an "access violation" message.
Further, i realize i can use idlasm to disassemble .net files, but it seems most of the more interesting dlls and files may be standard c dlls. How can i take a look at the code in these and modify if wanted?
thanks much.

farseer: what level of experience do you have?
V

I'd like to think i am decent developer, but that may be in my own mind
However, i do not do a lot of "hacking", i.e., have not had the need to do much reverse engineering. I have been coding ground up apps for over 10 years however, uisng C++, Java, C#, VB, etc. You name the language, and i've probably done something in it .
vijay555 said:
farseer: what level of experience do you have?
V
Click to expand...
Click to collapse

was that the wrong answer?
farseer said:
I'd like to think i am decent developer, but that may be in my own mind
However, i do not do a lot of "hacking", i.e., have not had the need to do much reverse engineering. I have been coding ground up apps for over 10 years however, uisng C++, Java, C#, VB, etc. You name the language, and i've probably done something in it .
vijay555 said:
farseer: what level of experience do you have?
V
Click to expand...
Click to collapse
Click to expand...
Click to collapse

The correct answer should be "I know ARM assembler language, the structure of Win32 PE files, I know what is XIP DLL and why I cannot modify them directly, and I have read the WM5 source code".
In this case the process is simple - you decompile a DLL with IDA (www.datarescue.com), find the place you need, modify the code to suit your needs - and that is all. In most cases there is not enough place in DLL for your code, so you need to use virus-like techniques, my prefered method is to patch the code so that it loads my DLL and run it instead of original code. Or use some other hooking methods so that my code is executed instead of original.

Ah, thanks much, this was helpful. I do have a few follow up questions:
1. Is "Arm assembler" different than standard assembler? If so, any suggested readings?
2. There are some dlls that cannot be copied to my local pc (i get an access violation i believe). How does one extract an image of such dlls?
3. Where is the WM5 source code? and why would i need to read this to be able to hack/patch dlls?
thanks again.
mamaich said:
The correct answer should be "I know ARM assembler language, the structure of Win32 PE files, I know what is XIP DLL and why I cannot modify them directly, and I have read the WM5 source code".
In this case the process is simple - you decompile a DLL with IDA (www.datarescue.com), find the place you need, modify the code to suit your needs - and that is all. In most cases there is not enough place in DLL for your code, so you need to use virus-like techniques, my prefered method is to patch the code so that it loads my DLL and run it instead of original code. Or use some other hooking methods so that my code is executed instead of original.
Click to expand...
Click to collapse

Hi farseer!
I am nowhere near the level of mamaich or vijay555 but I have some experience in this and I believe I can give you some basic answers:
1. ARM is a different architecture then x86 processors and the assembler is different to accommodate it. There are some basic similarities like mov add and such, but even the registers are different (R0 - R15 if I am not mistaken). Sorry, I don't know any books on it, but if you google you will quickly find the list of commands with basic explanation.
2. Since the OS is in ROM you can't just copy and paste it's DLLs and EXEs. Look for ROM dumping tools on this forum, or already extracted images on the ftp. Keep in mind MS did some tricks to save memory and make it harder to get at the files, so like mamaich said, you need to learn about XIP and the ROM structure in general to understand whats going on.
3. Hmm... MS does have a program for sharing most of WM source code, but it's not for common people like us. (check out their site to see what I mean) I suspect there are other sources of getting the parts necessary to understand DLL hooking, but I have no idea what they might be.
Well that's my two cents until an expert can answer you. Hope this helps.

farseer: you gave a perfectly good answer IMHO, just needed to get an idea of what level to pitch a response without talking up or down to you!
It's well documented that I'm a self confessed newb to c++, and would say that your programming skills should certainly hold you in good stead. However, having a good knowledge of the Win32 API is certainly beneficial.
For decompiling, basically IDA. There is an IDA demo available on their website that should get you going, it's pretty much 100% functional other then it won't save, and closes itself (or crashes itself) after a reasonable, random period of time. IDA is "the daddy" for pretty much all mainstream reversing, although you could write your own decompiler/debugger.
Recompiling - that's a toughy. IDA won't permit recompiling on ARM AFAIK.
You'll have to hexedit into the target and patch directly. Otherwise you get into the exciting world of code injection, hooking etc, as Mamaich says.
For that area, read everything he's ever written, before you start reversing
Oh, and a helpful hint to all. Don't just read what Mamaich's written on this board, his posts on other boards are even more useful!
It's worth getting a good familiarity with reversing on x86 first, get used to how IDA works etc (and Soft Ice is very useful to give a good insight into x86, although AFAIK it's not available for WinCE). ARM assembler is different, but just grab a list of the opcodes and read through a few CPU developers' guides (online).
There are a number of tutorials on reversing ARM stuff online. In the usual places for that kind of stuff.
For getting access to the ROM files, easiest way is to grab a rom update file and decrypt it. Mamaich is once again your man, his romtools do the job. He also has a "live" rom grabber, that'll grab all the files/modules out of your running phone for your perusal.
Platform Builder is available free to give you (some) WinCE source code. Not all, but enough to give you years worth of reading.
V

Thanks all...very kind of you to respond in such detail. I look forward to dabbling a bit with IDA and some of mamaich tools. I suppose the first order of business is to do a lil more research and then just dive in! It's been a while since i wrote any assembly code (not since college!), but i am a bit excited at having an excuse to do so again.
thanks again.

Just remember that unless you really luck out and the developer left the symbol table intact, you're going to end up with garbage for the names of variables and subroutines.
I hate reading decompiled code.

Leading underscore in function name

Hi!
I try to integrate an external library into my vs2005 project while using the Windows Mobile 6 SDK. Of course, I added the additional directories and dependencies to the project settings, but I get some LNK2019 errors anyway.
So I created a dump of the *.lib files using "dumpbin.exe" and discovered that all function names start with a leading underscore. I found some precompiled parts of the library where there are no leading underscores in the function names and I can call them without any problems. But if I build those parts of the library on my own, there again are the LNK2019 errors and the "_functionname()" convention in the *.lib files.
Is there either a way to avoid those underscores when compiling the library or to call those function out of a windows mobile application?
Thanks in advance!

This looks a bit odd.
C++ decorates exported functions unless you add a def file to the project, but there is always way more garbage in the names.
What I don't understand is, why do you have a problem using a function that starts with an underscore?
Such names are perfectly acceptable in C / C++, in fact some C native functions like _wfopen start with an underscore.
What language are you programming in?
Also it might help find the solution, if you tell us what library you are using. Is it something available for download or your own creation?

Thanks for your quick reply.
I am working on a porting of the intel openCV computer vision library and I try to include it into a VS2005 C++ projekt created with the wizard for windows mobile 6.0 sdk for testing.
It seems that the problem appears when I switch the system to "/SUBSYSTEM:WINDOWSCE". Otherwise the library works perfectly.

[XAP][SOURCE] Native Toast Notification Launcher

This is a very simple application that enables you to specify any kind of Uri to launch. This is done through creating a Toast notification that, when clicked on, will execute the specified Uri. This uses a native method outside of the regular SDK; the standard methods available in the SDK that you'd normally use to create a Toast notification are restrictive in what kind of Uri you can specify. By using the native method not part of the SDK, these limitations can be by-passed.
I've attached both the XAP and the source code. The source project contains three projects:
CShellChromeAPI: The C++/CLI project which calls the native un-documented method
NativeToastLauncher: The .NET wrapper which simplifies the interaction with the C++/CLI project
NativeToastLauncherApp: The test application used to quickly launch any Uri
You'll notice I've hard-coded a default Uri when you launch the application: this will open the Windows Phone 8 "About" page.
To run this, you'll need to side load the XAP which requires a dev unlocked device...

Can I use any system GUID to launch?

djtonka said:
Can I use any sytem GUID to launch?
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Click to collapse
Any registered app GUID yes. You'd do app://GUID/_default (or replace the _default with the particular task to run - in most cases, that's _default).

@cpuguy this is awesome, thanks!

If you guys are looking for GUIDS and default tasks, they are all in the app's WMAppMAnifest.xml. the "ProductID" is the GUID and the "DefaultTask Name" property contains the name of the default task.

Hopefully we can use this to find a program to exploit.
Sent from my Nokia 521 using XDA Windows Phone 7 App

Does anyone happen to have a list of the ID's for the system and settings apps? Obviously, I can't go into the code and get these without messing with the file system. If no one has them, then I can just trial/error until I get some...

If you download the registry hives located at http://forum.xda-developers.com/showthread.php?t=2393883 , you can load the Software hvie and search for "app://" That will give you a few system files you can launch.
EDIT:
I posted a zip file of the default ones in a new thread.
IF anyone has tethering blocked, see if you can get it to work by launching this URI app://5B04B775-356B-4AA0-AAF8-6491FFEA5629/Default

compu829 said:
If you download the registry hives located at http://forum.xda-developers.com/showthread.php?t=2393883 , you can load the Software hvie and search for "app://" THat will give you a few system files you can launch.
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Click to collapse
Im only seeing the app:// function used on the system settings options after going through the regsistries so far.

aclegg2011 said:
Im only seeing the app:// function used on the system settings options after going through the regsistries so far.
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Click to collapse
that's what I saw too. I am having way more luck finding cool stuff in the extracted ffu. Take a look at the zip file in the new thread I started.

compu829 said:
that's what I saw too. I am having way more luck finding cool stuff in the extracted ffu. Take a look at the zip file in the new thread I started.
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Click to collapse
yea, I saw the new thread. Hopefully somebody can find a exploit in all that. It executes some cool files. Too bad there wasn't a cmd.exe file on our phones that we can execute.

aclegg2011 said:
yea, I saw the new thread. Hopefully somebody can find a exploit in all that. It executes some cool files. Too bad there wasn't a cmd.exe file on our phones that we can execute.
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Click to collapse
actually..there is! but it's stuck in a WIM. It inflates it on an "as-needed" basis.
I am hoping that we can use the backgroundworker to run some stuff elevated

compu829 said:
I am hoping that we can use the backgroundworker to run some stuff elevated
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Click to collapse
But they all are pretty much isolated. It is unlikely that you will be able to run anything elevated

aclegg2011 said:
yea, I saw the new thread. Hopefully somebody can find a exploit in all that. It executes some cool files. Too bad there wasn't a cmd.exe file on our phones that we can execute.
Click to expand...
Click to collapse
Not only is there a CMD.exe, but there are other interesting things like a BSOD screen, Control Panel, registry keys referencing desktop (A future exploit I might attempt), and even native EXEs (We knew about native EXEs since WPs release).

Why does this launcher not work with "normal" toasts: {YOUR-APP-GUID} and "/Page1.xaml"? Only with empty GUID and full path.

Similarly, any chance this could be used to open arbitrary XAML pages, rather than just the ones defined in the app manifest? For example, something like what was posted in another thread (http://forum.xda-developers.com/showpost.php?p=45265419&postcount=56) using the following URI: app://5edbdbbc-2ab2-df11-8a2f-00237de2db9e/_default#/View/APNSettingPage.xaml to launch a hidden page in the Connection Setup app. I don't know if that's a weird behavior of CS or if its universally possible (and while it feels lazy to ask, I'm at work right now). There are a bunch of "hidden" pages in the ATIV S Diagnosis app, some of which would be very useful, but the navigation code for them is blocked or outright missing. If we could invoke those directly... There are probably a bunch of other such hidden gems in other OEM apps too.

Yes you can. The way I found the one in the HTC app was by loading the dlls in JetBrain's dotPeek. Then I looked for the xaml files. It is all a relative URI based on what dotPeek/the app "sees". The only thing the manifest states is where the default entry point is for the page. Basically I looked in the manifest file for how it calls the "default" page. and then replace it with the relative URI for the other page you want.
If you guys want, I can write up a simple tutorial. I just have an HTC 8x, so my hands are tied. If someone can figure out how to deflate an nbh file so I can browse it, that'd be fantastic! I found a "dead" 521 on eBay that I am thinking of picking up for research since there are way more tools for Nokia.

compu829 said:
Yes you can. The way I found the one in the HTC app was by loading the dlls in JetBrain's dotPeek. Then I looked for the xaml files. It is all a relative URI based on what dotPeek/the app "sees". The only thing the manifest states is where the default entry point is for the page. Basically I looked in the manifest file for how it calls the "default" page. and then replace it with the relative URI for the other page you want.
If you guys want, I can write up a simple tutorial. I just have an HTC 8x, so my hands are tied. If someone can figure out how to deflate an nbh file so I can browse it, that'd be fantastic! I found a "dead" 521 on eBay that I am thinking of picking up for research since there are way more tools for Nokia.
Click to expand...
Click to collapse
That's correct. I have been navigating to various - normally unreachable - XAML pages in quite a few of the Nokia apps. I gave an example of that in a different thread:
Code:
app://[COLOR="Navy"][B]2377fe1b-c10f-47da-92f3-fc517345a3c0[/B][/COLOR]/[COLOR="Orange"][B]_default[/B][/COLOR]#/[COLOR="Green"][B]Launcher[/B][/COLOR];component/[COLOR="DarkRed"][B]MainPage.xaml[/B][/COLOR]
In this example, I launch the Nokia extras+info app (2377fe1b-c10f-47da-92f3-fc517345a3c0) with the default entry point (_default) which, as @compu829 stated, can found in the app's manifest. Following that, you can add "#/" (not sure if either the hash-tag or slash can be taken out or both are required to work but I know with both, it does work) to the URI to specify a particular XAML file you'd like to open. Following the "#/", you get to specify the assembly (i.e. the .DLL in the XAP file) in which the XAML file is located (Launcher). And finally, you add ";component/" followed by the full path to the XAML as defined in the embedded resource file (MainPage.xaml).

-W_O_L_F- said:
Why does this launcher not work with "normal" toasts: {YOUR-APP-GUID} and "/Page1.xaml"? Only with empty GUID and full path.
Click to expand...
Click to collapse
I presume your reference to the "empty GUID" is for the first parameter of my static Launcher.LaunchToast method? That first parameter is, as far as I can see, ignored for the actual toast launch. If I'd have the signature of the "Shell_PostMessageToast" method, I could perhaps understand what it does but, without it, I just knew it wanted a GUID (passed to it as a string) and that that GUID could be an empty one. I reversed engineered the signature from that native method (found in ShellChromeAPI.dll) by taking a look at another native assembly calling it. Naturally, this only tells shows me how that method is being called but doesn't return the name of the parameters. If I remember correctly, the assembly calling that method was passing its own application GUID... I could have done the same but, I didn't see what use it had so I decided to keep passing it an empty GUID.
The format of the toast is different most likely because that's the raw toast launching method. The other format you're used to is the more developer friendly one that's sanitized prior to launching it (so you can't launch another app directly).

Success!
@GoodDayToDie , this is exactly what I'm trying to do! And here is result:

Successfully got my app with restricted API published in store !!

That's an app to help you lock screen and adjust volume with tiles. It calls functions in ShellChromeAPI.dll . Finally, it got published with English version.
link: http://www.windowsphone.com/en-us/store/app/quick-tiles/1725cca2-2349-4d33-b5d5-8b04e7810c04
(You may need to switch your phone language to English to download the English version. otherwise, the Chinese version will be shown. Forgive me for my tight schedule and I have to split different languages into different XAPs, for I only spent 2 hours developing this app...)
I've found two ways to pass the marketplace API detect, one is to use P/Invoke and the other is to load LoadLibraryExW without extern that from the lib provided by Microsoft.
both methods will be provided here in a month, and I may provide write some wrappers or static libraries.
Notice that I only found ways to access restricted API, but get higher privilege is not possible.
By this way, I think @GoodDayToDie 's HTTP Server with registry browser can be published with some simple modify. Even publishing the samsung interop unlock guide, which launches the toast using undocumented, is possible. Maybe we should try to find more useful functions which can be called without privilege in different dlls.

hjc4869 said:
That's an app to help you lock screen and adjust volume with tiles. It calls functions in ShellChromeAPI.dll . Finally, it got published with English version.
link: http://www.windowsphone.com/en-us/store/app/quick-tiles/1725cca2-2349-4d33-b5d5-8b04e7810c04
(You may need to switch your phone language to English to download the English version. otherwise, the Chinese version will be shown. Forgive me for my tight schedule and I have to split different languages into different XAPs, for I only spent 2 hours developing this app...)
I've found two ways to pass the marketplace API detect, one is to use P/Invoke and the other is to load LoadLibraryExW without extern that from the lib provided by Microsoft.
both methods will be provided here in a month, and I may provide write some wrappers or static libraries.
Notice that I only found ways to access restricted API, but get higher privilege is not possible.
By this way, I think @GoodDayToDie 's HTTP Server with registry browser can be published with some simple modify. Even publishing the samsung interop unlock guide, which launches the toast using undocumented, is possible. Maybe we should try to find more useful functions which can be called without privilege in different dlls.
Click to expand...
Click to collapse
What restricted API's possible to upload ?

ngame said:
What restricted API's possible to upload ?
Click to expand...
Click to collapse
you can load any API functions. but only some of them can be called and only a few is really useful.
I only tested the following functions
BOOL Shell_IsLocked()
void Shell_TurnScreenOn(BOOL)
void Shell_AdjustVolume(int)

hjc4869 said:
That's an app to help you lock screen and adjust volume with tiles. It calls functions in ShellChromeAPI.dll . Finally, it got published with English version.
link: http://www.windowsphone.com/en-us/store/app/quick-tiles/1725cca2-2349-4d33-b5d5-8b04e7810c04
(You may need to switch your phone language to English to download the English version. otherwise, the Chinese version will be shown. Forgive me for my tight schedule and I have to split different languages into different XAPs, for I only spent 2 hours developing this app...)
I've found two ways to pass the marketplace API detect, one is to use P/Invoke and the other is to load LoadLibraryExW without extern that from the lib provided by Microsoft.
both methods will be provided here in a month, and I may provide write some wrappers or static libraries.
Notice that I only found ways to access restricted API, but get higher privilege is not possible.
By this way, I think @GoodDayToDie 's HTTP Server with registry browser can be published with some simple modify. Even publishing the samsung interop unlock guide, which launches the toast using undocumented, is possible. Maybe we should try to find more useful functions which can be called without privilege in different dlls.
Click to expand...
Click to collapse
Interesting. But almost useless cause now all can freely make a developer unlock. Store apps can use RPC but this requires InteropServices CAP.

-W_O_L_F- said:
Interesting. But almost useless cause now all can freely make a developer unlock. Store apps can use RPC but this requires InteropServices CAP.
Click to expand...
Click to collapse
yes I tried it before in beta app .
ID_CAP_INTEROPSERVICES , Xbox live and exe files in xap are unable to upload !

And those APIs work without having the restricted capabilities in the manifest file?

After the update, it went back to Chinese... it would be nice if you set English as the default language, at least for European and American countries

mcosmin222 said:
And those APIs work without having the restricted capabilities in the manifest file?
Click to expand...
Click to collapse
Yes.

-W_O_L_F- said:
Yes.
Click to expand...
Click to collapse
Hmmm
This looks interesting.

P/Invoke? How did you manage to use it? I thought it was not available for Silverlight?

pinvoke is possible with silverlight, but according to microsoft it is illegal on the marketplace.
which is half true. you cant pinvoke a native dll compiled for arm, but the wp8 own dlls seem to make an exception

mcosmin222 said:
you cant pinvoke a native dll compiled for arm, but the wp8 own dlls seem to make an exception
Click to expand...
Click to collapse
What is the difference?

Useless guy said:
What is the difference?
Click to expand...
Click to collapse
Go ask microsoft.
If you scroll down you will find that p/invoke is not allowed in wp8 sdk
http://msdn.microsoft.com/en-us/lib...jj206940(v=vs.105).aspx#BKMK_Appcompatibility
however, the OP seems to have managed to do it with a DLL contained in the WP8 system.
I never actually tried to p/invoke something on the marketplace. Maybe this needs additional research to see if arm compiled third party dlls can be used.
I remember some guy on the forum trying to p/invoke a native ARM dll and got type load exceptions.
by native i mean something which is not compiled with C++/CX for windows phone. As in pure C/C++ targeted for ARM.

mcosmin222 said:
Go ask microsoft.
If you scroll down you will find that p/invoke is not allowed in wp8 sdk
http://msdn.microsoft.com/en-us/lib...jj206940(v=vs.105).aspx#BKMK_Appcompatibility
however, the OP seems to have managed to do it with a DLL contained in the WP8 system.
I never actually tried to p/invoke something on the marketplace. Maybe this needs additional research to see if arm compiled third party dlls can be used.
I remember some guy on the forum trying to p/invoke a native ARM dll and got type load exceptions.
by native i mean something which is not compiled with C++/CX for windows phone. As in pure C/C++ targeted for ARM.
Click to expand...
Click to collapse
I know what pinvoke is perfectly, don't send me to msdn as long as I'm able to find it by myself.
Both an unmanaged dll and a WinRT component are native. CLR wraps every COM\WinRT object in the Runtime Callable Wrapper, but the object itself stays in the unmanaged heap.
If you think that WinRT or C++/CX are not native, you're wrong.
To @hjc4869
How did you manage to bypass marketplace analysis using P\Invoke? I'm fairly certain that MS checks metadata for DllImport attribute.
I'm going to try the second way, thanks!

Useless guy said:
I know what pinvoke is perfectly, don't send me to msdn as long as I'm able to find it by myself.
Both an unmanaged dll and a WinRT component are native. CLR wraps every COM\WinRT object in the Runtime Callable Wrapper, but the object itself stays in the unmanaged heap.
If you think that WinRT or C++/CX are not native, you're wrong.
To @hjc4869
How did you manage to bypass marketplace analysis using P\Invoke? I'm fairly certain that MS checks metadata for DllImport attribute.
I'm going to try the second way, thanks!
Click to expand...
Click to collapse
never said you don't know what p/invoke is.
I just wanted to show you that it is illegal in wp8 SDK (which that link leads to).
And if you actually read that link, you would see that invoking winRT or C++/CX (compiled for WP8) is allowed. This is probably due to the fact that these methods still execute in a sandbox. While MS won't allow arm compiled dll without the WP8 SDK because it can't verify its security.

mcosmin222 said:
And if you actually read that link, you would see that invoking winRT or C++/CX (compiled for WP8) is allowed. This is probably due to the fact that these methods still execute in a sandbox. While MS won't allow arm compiled dll without the WP8 SDK because it can't verify its security.
Click to expand...
Click to collapse
What does it mean - compile for WP8? I can add to the package any dll that uses Win32 (non-restricted) and compiled for ARM. The library will work on both WP and W8 without recompilaton.

Useless guy said:
What does it mean - compile for WP8? I can add to the package any dll that uses Win32 (non-restricted) and compiled for ARM. The library will work on both WP and W8 without recompilaton.
Click to expand...
Click to collapse
Will it? When you compile a C++ dll for desktop, it references kernel32.dll and unless you explicitly exclude it from the linker, it couldn't possible work on WP8 since there's no kernel32.dll.

Hi all
Trying to play with this method, but it seems LoadLibraryExW is not available. The only function available is LoadPackagedLibrary and when I try to run it, I've got C00000D error which is STATUS_INVALID_PARAMETER.
---------- Post added at 01:03 PM ---------- Previous post was at 12:49 PM ----------
It seems LoadPackagedLibrary only loads .dll from installation folder of application and do not allows full path in name. Thats why I got invalid argument error

Useless guy said:
What is the difference?
Click to expand...
Click to collapse
Code signature.

Sunius1 said:
Will it? When you compile a C++ dll for desktop, it references kernel32.dll and unless you explicitly exclude it from the linker, it couldn't possible work on WP8 since there's no kernel32.dll.
Click to expand...
Click to collapse
Kernel32.dll is the huge part of Win32 and it exists on both WP and Windows. WPSDK doesn't include kernel32.lib, but I'm pretty sure it can be easily generated from dll file.
#define WINAPI_PARTITION_DESKTOP and kernel32.lib should work, I think.
UPD:
I forgot, kernel32 could be removed as it's just the compatability layer for kernelbase.dll and new windows 8 api sets (api-ms-*.dll).
clrokr said:
Code signature.
Click to expand...
Click to collapse
DLLs are signing on certification process.

C++: open file for writing in the LocalStorage

Hi guys, could you tell me how to open file for writing in the phone app LocalStorage for the non-unlocked handset (regular app for store)?
Code below doesn't work
Code:
FILE *tmp;
auto tmpPath = Windows::Storage::ApplicationData::Current->LocalFolder->Path + "\\tmp.txt";
auto tmpErr = _wfopen_s(&tmp, tmpPath->Data(), L"w");
Any suggestions?

Try looking though msdn articles. I found it somewhere in there. But I have forgotten it now.
Sent from Board Express on my Nokia Lumia 1020. Best phone ever!!
Note to noobs: DON'T PM ME WITH QUESTIONS. POST IN THE FORUMS. THAT'S WHAT THEY ARE HERE FOR!

@wcomhelp, please keep your rtfm advices for yourself, OK? I'm not a noob and of course I've searched msdn, google, codeplex, github etc. and so on before posting here. If you don't know how, much better be silent (like others who read this post but have no idea what I'm talking about)
I've tried a few possible methods including ugly "MS-way" with task & lambda syntax (see below) but nothing worked as it should be (code below works if no file exist and fails if file already exist - CreationCollisionOption::ReplaceExisting options is not worked/not implemented/buggy/billgates_knows_only ).
Code:
auto folder = Windows::Storage::ApplicationData::Current->LocalFolder;
Concurrency::task<Windows::Storage::StorageFile^> createFileOp(
folder->CreateFileAsync(CONFIG_FILE_NAME, Windows::Storage::CreationCollisionOption::ReplaceExisting));
createFileOp.then([=](Windows::Storage::StorageFile^ file)
{
return file->OpenAsync(Windows::Storage::FileAccessMode::ReadWrite);
})
.then([=](Windows::Storage::Streams::IRandomAccessStream^ stream)
{
auto outputStream = stream->GetOutputStreamAt(0);
auto dataWriter = ref new Windows::Storage::Streams::DataWriter(outputStream);
// data save code skipped
return dataWriter->StoreAsync();
})
.wait();
BTW, I've used workaround, to save ported C++ app data to the LocalSettings instead of text file (as it was in original code).

"Doesn't work" doesn't give us a lot to go on, troubleshooting-wise. Can you tell us what error you get?
Only thing I see in the code that looks a little weird is that the
Code:
"\\tmp.txt"
part isn't explicitly a wide-character string, but I'd expect string concatenation to take care of that.
Also, out of curiosity, why libc functions instead of Win32? Obviously, the code you're writing here isn't intended for much portability...

@GoodDayToDie, there is no error code at all - standard POSIX functions returns NULL FILE, the ::GetLastError() also return 0.
I'm porting old C-style app to WinRT platform and don't care about portability (but the first post code - just a simplified example, nothing more).
POSIX (libc) functions works pretty well for reading only but not for writing - that's the problem...
As I said before, I resolved my issue by workaround but still curious why the POSIX calls fails for file writing in the app storage.

buuuuuuuuuuuuuuuuh
No need for lambdas
https://paoloseverini.wordpress.com/2014/04/22/async-await-in-c/
You may also want to rethink your strategy
You can't create files at arbitrary locations, so your method is kinda redundant. All the locations you are allowed to create and read files to/from are available through KnowFolders and ApplicationData classes. These return StorageFolders which in turn can create files with CreateFileAsync (used for both creating and opening existing files) and get files with GetFilesAsync ( I recommend against this one though) and similar methods.

@mcosmin222, could you please re-read my posts one more time? I'm not trying to create files at "arbitrary locations"; I wanna create/write simple text file at the app's local storage (which one should be available for reading/writing). And the problem not in the lambdas or task usage (yes, it looks ugly but it works as it supposed to be).
Could you provide a working example instead of words? And I'll be glad to say you "thanks a lot"; can't say now...

sensboston said:
@mcosmin222, could you please re-read my posts one more time? I'm not trying to create files at "arbitrary locations"; I wanna create/write simple text file at the app's local storage (which one should be available for reading/writing). And the main problem not in the task (async execution).
Could you provide a working example instead of words? And I'll be glad to say you "thanks a lot"; can't say now...
Click to expand...
Click to collapse
Sure, just gimmie a few hours till I can get near a compiler that is capable of doing that

Of course, no rush at all, take your time. It's not a showstopper for me now (actually, my workaround with AppSettings is more preferable way - at least for universal app and roaming settings) but the issue still has an "academic interest" and maybe will be useful in the next projects for porting old C/C++ code to WinRT.

sensboston said:
Of course, no rush at all, take your time. It's not a showstopper for me now (actually, my workaround with AppSettings is more preferable way - at least for universal app and roaming settings) but the issue still has an "academic interest" and maybe will be useful in the next projects for porting old C/C++ code to WinRT.
Click to expand...
Click to collapse
hi
in vs 2015
#include <pplawait.h>
Something of the like should work
Code:
WriteSomeFile() __resumable
{
auto local = ApplicationData::Current->LocalFolder;
auto file = __await local->CreateFileAsync("some file", CreationCollisionOption::eek:penIfExists);
__await FileIO::WriteTextAsync(file, "this is some text");
}
However, as of right now, in VS 2015 RC, you have a host of limitations when dealing with this, but I do not believe this will be of any issue to you.
Code:
Cannot use Windows Runtime (WinRT) types in the signature of resumable function and resumable function cannot be a member function in a WinRT class. (This is fixed, but didn't make it in time for RC release)
We may give a wrong diagnostic if return statement appears in resumable function prior to seeing an await expression or yield statement. (Workaround: restructure your code so that the first return happens after yield or await)
Compiling code with resumable functions may result in compilation errors or bad codegen if compiled with /ZI flag (Edit and Continue debugging)
Parameters of a resumable function may not be visible while debugging
Please see this link for additional details
http://blogs.msdn.com/b/vcblog/archive/2015/04/29/more-about-resumable-functions-in-c.aspx
you should also note that this works with native, standard C++ types.

@mcosmin222, looks like unbuffered writing works (i.e. without streams) fine but it still not an answer for my initial question
I'm curious why the standard POSIX libc writing operations are not working on the app's local storage (but reading from files works fine). Actually, it's all about porting old C/C++ code for WinRT; of course for the new app it's not a problem but re-writing old code to FileIO should be a huge pain in the ass. What I did: I've "mechanically" changed all libc formatted outputs from file to string, and use LocalSettings class (actually it's XML file) to store that string (I'm planning also change LocalSettings to RoamingSettings, to provide settings consistency between WP & desktop app).
P.S. <pplawait.h> is not available in my VS 2015 (release pro version) so I've tested by using lambda pattern.

OK, first things first, LIBC != POSIX! The POSIX way to do this would be to call the open() function and get back an int as an "fd" (file descriptor), which is of course not implemented on Windows Phone because Windows Phone is not a POSIX platform (you might find the Windows compatibility functions _open() and _wopen(), but I doubt it). You are attempting to use the standard C library functions, which are portable but implement kind of a lowest common denominator of functionality and are generally slightly slower than native APIs because they go through a portability wrapper.
Second, sorry to be all RTFM on you but you should really Read The Manual (or manpage, or, since this is Windows, the MSDN page)! Libc APIs set errno (include errno.h) and use different error values than Windows system error codes (or HRESULT codes, or NTSTATUS codes, or...). Error reporting in C is a mess. If you were calling CreateFile(), you would check GetLastError(), but since you're calling _wfopen(), you check errno (not a function).

@GoodDayToDie, _wfopen_s returns 0 (i.e. "no error") but tmp pointer receives also 0 (NULL) Could you explain why libc file functions are working for reading (at the app installation & local data folders of course) but not for writing? Any logical ("msdn based") explanation? Or you just... don't know, heh?

sensboston said:
@GoodDayToDie, _wfopen_s returns 0 (i.e. "no error") but tmp pointer receives also 0 (NULL) Could you explain why libc file functions are working for reading (at the app installation & local data folders of course) but not for writing? Any logical ("msdn based") explanation? Or you just... don't know, heh?
Click to expand...
Click to collapse
LIBC functions will most likely work just in debug mode. The moment you try to publish the app it will fail. You can do lots of crazy stuff on your developer device with basic C functions, but if you try publishing, it won't pass the marketplace verification.
Most C APIs are simply not supported, since they do not comply with the sandbox environment of the Windows Runtime.
The code I gave you is tested with VS 2015 RC. You should be able to include <pplawait.h> just fine, if you are targeting toolchains newer than November 2013.

mcosmin222 said:
The moment you try to publish the app it will fail. You can do lots of crazy stuff on your developer device with basic C functions, but if you try publishing, it won't pass the marketplace verification.
Click to expand...
Click to collapse
Hmm... Are you sure or it's just your assumption? My app is still under development but (just for test!) I've made store app package for WP and it passed local store verification I also uploaded package to the store (via browser) and it also passed. I don't have time to create all tiles and fill all fields to complete beta-submission (actually, I don't know how to mark app as beta in the new dashboard) but for me it looks like app don't have any problem and will pass store certification easily. And you may be sure - it uses A LOT of libc calls 'cause originally it was written for Linux (or kind of UX system)

sensboston said:
Hmm... Are you sure or it's just your assumption? My app is still under development but (just for test!) I've made store app package for WP and it passed local store verification I also uploaded package to the store (via browser) and it also passed. I don't have time to create all tiles and fill all fields to complete beta-submission (actually, I don't know how to mark app as beta in the new dashboard) but for me it looks like app don't have any problem and will pass store certification easily. And you may be sure - it uses A LOT of libc calls 'cause originally it was written for Linux (or kind of UX system)
Click to expand...
Click to collapse
Once usage reports get up to microsoft, you will be given a notice to fix the offending API (happened to be once). You are much better off using the platform specific tools: not only they are much faster, they are also much safer and you won't have problems later on.
You might get away with reading stuff (since reading is not that harmful), but you should be using the winRT APIs each time they are available.
Simply uploading your app to the marketplace just reruns the local tests in their cloud servers: once you submit the actual app (not beta, not tests) for consumers, it will be much more aggressively checked. This is because the store allows specific scenarios for distributing apps in close circles that may break the usual validation rules.

@mcosmin222, one more time: is it your assumptions or personal experience? I don't know how many apps you have in store (I do have a lot) but I never heard that you said. I've used C++ libraries with WP hacks in some of published apps but never had any problem with "aggressive checks". What I know: if you are using some "prohibited" calls, your app will not pass uploading to the store (uploading, not a certification).
P.S. I'll send you personally a link when I publish release Hope, you'll like it

sensboston said:
@mcosmin222, one more time: is it your assumptions or personal experience? I don't know how many apps you have in store (I do have a lot) but I never heard that you said. I've used C++ libraries with WP hacks in some of published apps but never had any problem with "aggressive checks". What I know: if you are using some "prohibited" calls, your app will not pass uploading to the store (uploading, not a certification).
P.S. I'll send you personally a link when I publish release Hope, you'll like it
Click to expand...
Click to collapse
By "hacking" you mean recompiling the code to fit the windows phone toolchain? if so, then you shouldn't have to worry about too many things.
but even so, calling stuff like fopen in locations other than local storage will get your app banned. Even if it makes past the first publication, you can get noticed weeks later or even months (yes, it did happen to me personally).
In most cases, calling C APIs that can potentially break the sandbox (like opening a file in doc library with fopen) will always fail the marketplace verification, eventually. If it hasn't happened to you yet, then you may have not been using such APIs.

No, my C++ code is not accessing other than approved locations but the app has a lot of libс (and of course other C/C++ libs) calls; I'm 99.9% sure it's legitimate and will be not a source of any problem. Otherwise what is the advantages of having C++ compiler?!
As far as I know, just some of API's are prohibited but you will notice it right after local store compatibility test run...
As for "hacks" I mean usage of undocumented ShellChromeAPI calls (including loading hack).
P.S. I've found why <pplawait.h> header is missing. Initially I've created solution with the 12.0 toolset but now I can't (or don't know how to) change it to 14. However creating the new empty universal solution in VS 2015 also gives me toolset 12 by default. What is the toolset 14 for? Windows 10?

sensboston said:
No, my C++ code is not accessing other than approved locations but the app has a lot of libс (and of course other C/C++ libs) calls; I'm 99.9% sure it's legitimate and will be not a source of any problem. Otherwise what is the advantages of having C++ compiler?!
As far as I know, just some of API's are prohibited but you will notice it right after local store compatibility test run...
As for "hacks" I mean usage of undocumented ShellChromeAPI calls (including loading hack).
P.S. I've found why <pplawait.h> header is missing. Initially I've created solution with the 12.0 toolset but now I can't (or don't know how to) change it to 14. However creating the new empty universal solution in VS 2015 also gives me toolset 12 by default. What is the toolset 14 for? Windows 10?
Click to expand...
Click to collapse
The advantage of C++ is the obvious versatility: the standard C++ APIs will work fine for you as long as you stay inside the sandbox (this means you can't access files even in locations that are outside of sandbox but you have permission to them, such as music library). You can use most classic C/C++ libraries without issues as long as you do the interface with the runtime broker yourself. That means using windows runtime APIs instead of classic C APIs when dealing with stuff such as file access, for example. This is a pretty extensive topic and It is rather difficult to explain it all with 100% accuracy, especially when there is lots of docs running around.
You also get deterministic memory management, which is huge in specific scenarios.
Long story short
You will be fine with standard C/C++ when using
any in-memory functions supported by the compiler (you can manipulate data types, string, mutex, etc).
File IO in isolated storage only (applicationData folder)
Threads (although you are better off using threadpool or the like, it is much easier and cleaner). You can also use futures, and std::this_thread.
You will have to use winRT replacement
File system access in any other location than application data (you must use the windows::storage APIs)
sockets, internet access and the like.
any hardware related thing: music&video playerback must be interfaced through winRT (although the underlying decoders can be classic C/C++), messing around with the device sensors.
Retrieving system properties (internet connection state etc)
cross process communications
communicating with other apps
There are also win32 equivalents
mutex, threading, fileIO (isolated storage only)
Media playback with custom rendering pipeline.
Basically, winRT functions as an abstraction layer between the hardware and your code. You can use classic C++ up to the point where you need to interact with the system in any way. At that point, system interaction must be done with winRT. This way, microsoft ensures a higher degree of stability and security for devices.
check this link out for more information on the toolchains. You should be able to use this in VS 2013 as well with windows 8 (this is a compiler feature, has nothing to do with supported platform)
https://paoloseverini.wordpress.com/2014/04/22/async-await-in-c/