[xmlsec] Re: problem encrypting when using Windows 2000 ?

Aleksey Sanin aleksey at aleksey.com
Wed Jan 8 08:28:28 PST 2003


Thanks for long explanation! Will you mind if I add this to the FAQ?
I think this will be helpfull for people and save some time for us :)


Igor Zlatkovic wrote:

> Hi Aleksey,
> Those pointers being garbage is most often caused by static link 
> without #defining XMLSEC_STATIC. Another pitfall is using the wrong C 
> runtime. It is time for another lenghty explanation :-)
> *STATIC Macros
> --------------
> When people link statically to libxmlsec, then they must #define 
> XMLSEC_STATIC in their source files before including any xmlsec 
> header. I observe, almost noone is doing that. This macro has no 
> effect on Unix, but it is vital on Windows.
> This applies to libxml and libxslt as well, no matter if these are 
> used directly or not. If just libxmlsec is used, but everything is 
> linked statically, then there must be a
>   #define LIBXML_STATIC
>   #define LIBXSLT_STATIC
>   #define XMLSEC_STATIC
> before any xmlsec header is included. Even if the client code doesn't 
> call into libxml at all, still this must be defined. Xmlsec headers 
> will include libxml headers and they must have these definitions. 
> Without them, every variable xmlsec includes from libxml headers will 
> have __declspec(dllimport) prepended and that will give headaches if 
> static libxml is used for linking.
> This scheme makes it possible to have any combination of static and 
> dynamic libraries in the resulting executable. Its cost is the need to 
> #define apropriate macros. People would ideally define them by using 
> the compiler's /D switch in projects that link statically.
> Note that all this mess originates in MS linker and its inability to 
> import a variable from a DLL if that variable isn't declared with 
> apropriate declaration modifier. Since I cannot think of a good reason 
> for the existence of this requirement, I consider it a bug in MS linker.
> MS C Runtime
> ------------
> Windows basically has two C runtimes. The one is called libc.lib and 
> can only be linked to statically. The other is called msvcrt.dll and 
> can only be linked to dynamically. The first one occurs in its 
> single-threaded and multithreaded variant, which gives three different 
> runtimes. These three then live in their debug and release 
> incarnations, which results in six C runtimes, five of which are 
> designed just to increase overall confusion :-)
> The art is to choose the right one.
> libxml, libxslt and libxmlsec, as I compile them, are all linked to 
> msvcrt.dll. The click-next click-finish wizardry from Visual Studio 
> chooses the single-threaded libc.lib as the default when you create a 
> new project. Using my binaries with that default is asking for 
> trouble. The program will crash as soon as the two runtimes meet.
> The rule is simple. Exactly the same runtime must be used throughout 
> the application. Client code must use the same runtime as libxmlsec, 
> libxml and libxslt. This means, /MD compiler switch must be present 
> when compiling anything related to the binaries I provide. If someone 
> needs a different runtime for some reason, then the one must recompile 
> not only libxmlsec, but libxml and libxslt, perhaps even openssl as well.
> Ciao,
> Igor
> Aleksey Sanin wrote:
>> Igor,
>> Thanks for looking into this! I believe that there is a problem with
>> exporting pointers from dlls. In xmlsec I have static objects in the
>> DLL and I export pointers to these objects. The error Meg and
>> some other folks have is caused by the fact that these pointers are
>> NULL in the application (or point to garbage in some cases).
>> AFAIK, libxml and libxslt does not use such technique and there is
>> no surprise that your binaries work just fine for these libraries :)
>> When it's a simple and clear operation on *nix, it seems to be a problem
>> on Windows because of the compiler(s), compiler options or whatever.
>> I am working on fixing this but this will have to wait till the big new
>> release because of binary compatibility issues.
>> Aleksey
>> Igor Zlatkovic wrote:
>>> Hi Meg,
>>> I tried and tried, but wasn't able to reproduce that error.
>>> I use a slightly newer compiler than you do. As far as I know, the 
>>> binaries produced by that compiler are fully compatible with those 
>>> produced by VC 6. There should be no problems.
>>> However, there are some, obviously. Things might go good if you 
>>> recompile xmlsec with VC 6 but I fear that is not the root of the 
>>> problem. After all, libxml and libxslt binaries on my site are made 
>>> with the same compiler, are being downloaded fifty times a day in 
>>> average and many who use them do it with VC 6. The problem never 
>>> occured in a package other than xmlsec.
>>> I believe that the best way is to find the real source of the peril. 
>>> If it is in the xmlsec code, it must be fixed. If you did something 
>>> wrong in your code, then few others are obviously doing the same and 
>>> it should be discovered what that is. Finally, if the compiler is 
>>> the problem, then I'll start making binaries with VC 6.
>>> I have produced xmlsec 0.0.11 with VC 6 for you to test. You can get 
>>> it at
>>> http://zlatkovic.com/projects/libxml/libxmlsec-0.0.11.win32.vc6.zip
>>> Check if that one works.
>>> If you have code which demonstrates the error for me to use locally 
>>> for debugging, it would be very helpful.
>>> Ciao,
>>> Igor
>>> Meg Morgan wrote:
>>>> Greetings,
>>>> I understand from Alexsey that this problem has been reported before.
>>>> I am using your binaries and developing a windows application with
>>>> MS Visual C++ 6.0.  When I call xmlSecEncryptMemory I get an error:
>>>> xmlSecTransformFind <..\src\transforms.c:331>: error 10:  :
>>>>   href=http://www.w3.org/2001/04/xmlenc#tripledes-cbc
>>>> Alexsey writes:
>>>> "Let me guess, you are using Windows.
>>>> Most likely you are using Igor's Windows binaries with MS VC 6.0. 
>>>> There were reported similar problems in this situation and the best 
>>>> advise I can give is to try to recompile everything by you "native" 
>>>> compiler."
>>>> Is there any solution other than for me to compile under Windows 
>>>> myself?
>>>> Thank you for your help,
>>>> meg
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