Programming Forums > Application Development > C++

Frenchy · Aug 5th, 2004, 1:23 PM

how i know if i have a library compatible with DEV-C++, sometimes i use te tool reimport to convert microsoft obj library to library.a (format for DEV-C++)

but i 'd like to know if the result is good..?? :huh:

Frenchy

Ooble · Aug 5th, 2004, 1:44 PM

I don't know the answer, but welcome to the forums!

Infinite Recursion · Aug 5th, 2004, 3:37 PM

Although I have not done this personally... I can almost guarantee that the conversion from MS object code to any other via any tool, be it import or a third party app will not turn out very stable. The primary reason is that MS is proprietary and the MS object may reference components that are not known to a "foreign" compiler.

Someone else may be able to shed more light on the details for you.

Welcome to the forums!

kurifu · Aug 7th, 2004, 12:57 AM

MS's libraries (in C and C++ anyway) used a format called COFF. *.a format uses ELF (or does it? actually it may use the pre-elf old school UNIX/Linux format... but beside the point).

The formats should be able to import from MS's library format to the .a format SO LONG AS the functions being exported from MS's format contain functions that are not mangled... actually even mangled function should be exportable, they will probably just be uncallable by normal means.

C++ exported classes and functions will probably not import. Usually there is a verbose mode which will tell you when something will import or not. Just check the exported tables when you are done, make sure everything you needed is actually there. You will get unresolved externals otherwise when trying to link your code.

Frenchy · Aug 7th, 2004, 3:47 AM

thanks for your msg of welcome...

hum....
i am afraid the library what i want to use contains what you cll "mangled name"..

so i cant use tools to import DLL or to create importation lib format DEVC++ (DLLtool is a good example)

Quote:

LIBRARY SkunkCmp.dll
EXPORTS
??0CCat@@QAE@XZ
??0CChunkFile@@QAE@XZ
??1CCat@@QAE@XZ
??1CChunkFile@@QAE@XZ
??4CCat@@QAEAAV0@ABV0@@Z
??4CChunkFile@@QAEAAV0@ABV0@@Z
?AddChunk@CChunkFile@@QAEHKKPAXKH@Z
?CheckChunkFileSize@CChunkFile@@IAEHK@Z
?Close@CCat@@QAEXXZ
?Close@CChunkFile@@QAEXXZ
?ExpandFile@CCat@@SAHPAD0@Z
?ExtendFileSize@CChunkFile@@IAEHK@Z
?FindChunk@CChunkFile@@IAEPAUCHUNKREC@@KK@Z
?FreeAll@CCat@@QAEXXZ
?FreeFile@CCat@@IAEHPAUFILEHDR@@@Z
?FreeFile@CCat@@QAEHH@Z
?FreeFile@CCat@@QAEHPAD@Z
?GetCurrentFileSize@CChunkFile@@IAEKXZ
?GetFileCount@CCat@@QAEHXZ
?GetFileHdr@CCat@@IAEPAUFILEHDR@@H@Z
?Open@CCat@@QAEHPAD@Z
?Open@CChunkFile@@QAEHPADHK@Z

but that question so:

i if use VC++ how i can create an import lib from a DLL which already exist?? (in fact no available source).. with dev-C++ i use Dlltool but is there a tool as Dlltool to create a .lib ??

kurifu · Aug 7th, 2004, 12:54 PM

There is a way to do this.. but it is much more difficult.

What you need to do is create a project with VC++ which links to the DLL you are trying to export and creates a C style interface. It is not that difficult to do, though it is difficult to explain.

Lets say you have a class

class Foo1 { ... } exported from your MSVC DLL or Library, you will need to create a new project which links to the library and does the following:

(Toggle Plain Text)

extern "C" {
 __declspec( export ) void* CreateObject( );
 __declspec( export ) void DestroyObject( );

 __declspec( export ) int ThisWrapsAFunctionInTheClass( void* Object );
}

Essentially what you are doing is creating a wrapper which binds to the library and rexports all the methos through a C style (non-mangled) means. CreateObject create a new insatiation of the class and returns a pointer to the object, Destroy object delets it when you are done with it, and then you would write a function which takes the object and calls the corresponding function on the object and returns the value.

You can create a library with this new project you created which should be importable to DevC++, or even a DLL (though i do not recommend that since DLL-Proxies are memory inefficient).

Try googling "exporting C++ interfaces through C" or "flattening C++ dlls" if you find a few examples on the net, you are bound to understand the technique a bit better.

Aug 5th, 2004, 1:44 PM	#2
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	I don't know the answer, but welcome to the forums! __________________ Me :: You :: Them

Aug 5th, 2004, 3:37 PM	#3
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	Although I have not done this personally... I can almost guarantee that the conversion from MS object code to any other via any tool, be it import or a third party app will not turn out very stable. The primary reason is that MS is proprietary and the MS object may reference components that are not known to a "foreign" compiler. Someone else may be able to shed more light on the details for you. Welcome to the forums! __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Aug 7th, 2004, 12:57 AM	#4
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	MS's libraries (in C and C++ anyway) used a format called COFF. *.a format uses ELF (or does it? actually it may use the pre-elf old school UNIX/Linux format... but beside the point). The formats should be able to import from MS's library format to the .a format SO LONG AS the functions being exported from MS's format contain functions that are not mangled... actually even mangled function should be exportable, they will probably just be uncallable by normal means. C++ exported classes and functions will probably not import. Usually there is a verbose mode which will tell you when something will import or not. Just check the exported tables when you are done, make sure everything you needed is actually there. You will get unresolved externals otherwise when trying to link your code. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

Aug 7th, 2004, 12:54 PM	#6
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	There is a way to do this.. but it is much more difficult. What you need to do is create a project with VC++ which links to the DLL you are trying to export and creates a C style interface. It is not that difficult to do, though it is difficult to explain. Lets say you have a class class Foo1 { ... } exported from your MSVC DLL or Library, you will need to create a new project which links to the library and does the following: (Toggle Plain Text) extern "C" { __declspec( export ) void* CreateObject( ); __declspec( export ) void DestroyObject( ); __declspec( export ) int ThisWrapsAFunctionInTheClass( void* Object ); } extern "C" { __declspec( export ) void* CreateObject( ); __declspec( export ) void DestroyObject( ); __declspec( export ) int ThisWrapsAFunctionInTheClass( void* Object ); } Essentially what you are doing is creating a wrapper which binds to the library and rexports all the methos through a C style (non-mangled) means. CreateObject create a new insatiation of the class and returns a pointer to the object, Destroy object delets it when you are done with it, and then you would write a function which takes the object and calls the corresponding function on the object and returns the value. You can create a library with this new project you created which should be importable to DevC++, or even a DLL (though i do not recommend that since DLL-Proxies are memory inefficient). Try googling "exporting C++ interfaces through C" or "flattening C++ dlls" if you find a few examples on the net, you are bound to understand the technique a bit better. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

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Aug 5th, 2004, 1:23 PM	#1
Frenchy Newbie Join Date: Aug 2004 Posts: 10 Rep Power: 0	how i know if i have a library compatible with DEV-C++, sometimes i use te tool reimport to convert microsoft obj library to library.a (format for DEV-C++) but i 'd like to know if the result is good..?? :huh: Frenchy

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Programming Forums > Application Development > C++

Question About Obj Library