[gdal-dev] GDAL 1.8 - Switch Thrown

[Ari Jolma]

29.1.2011 20:43, Tamas Szekeres kirjoitti:
> Ari,
>
> I would be eager to know the exact use case you have. Did you have 
> some errors provided by the linker in this case?

For the stdcall functions I added entries like this

_CPLDefaultErrorHandler at 12
CPLDefaultErrorHandler = _CPLDefaultErrorHandler at 12

to the .def file. I create the .dll.a, which is the import library, with 
dlltool from the .def.

There are no errors from the linker. If I leave the stdcall entries as 
they are from pexports, i.e., just

_CPLDefaultErrorHandler at 12

The linker complains about undefined reference to `CPLDefaultErrorHandler'

However, running the Perl tests fail with "The procedure entry point 
CPLDefaultErrorHandler could not be located in the dynamic link library 
gdal17.dll". This is no wonder since the Perl bindings GDAL.dll imports 
CPLDefaultErrorHandler from gdal17.dll. I believe this because I'm 
misusing the .def file or dlltool does not understand that 
CPLDefaultErrorHandler is an alias to _CPLDefaultErrorHandler at 12.

I saw a web page which seemed to say that this is a known problem in 
dlltool and it had a small hack for dlltool.c to fix the problem, but I 
don't find the page just now and I've not yet tried hacking the 
dlltool.c (it seems quite possible).

I think the cdecl functions work ok.

If I compile GDAL in MSYS, all functions are exported cdecl.

Ari


> It would indeed be a problem how the various compilers decorate their 
> export functions in a different way. It looks like the 
> __declspec(dllexport) option (this is what is used in GDAL) provides 
> different names with MSVC and MinGW by default. If we want to compile 
> the dlls in a portable way we should probably get back to an 
> alternative method like .def file or "#pragma comment( linker, 
> "/export:FuncName" )" when exporting the functions.
>
> The article you are referring to describes another way of providing a 
> portable version that is:
> 1. Compile the dll as it is now (the functions exported 
> with__declspec(dllexport))
> 2. Extract the export functions in a .def file by using pexports
> 3. Replace the function names with their undecorated names in the .def 
> file
> 4. Recompile the dll with this new export definition file.
>
> I'm keen to give it a try if I get some further info about how to test 
> this on the other side.
>
>
> Best regards,
>
> Tamas
>
>
>
>
> 2011/1/29 Ari Jolma <ari.jolma at gmail.com <mailto:ari.jolma at gmail.com>>
>
>     Did anybody else try to use the now standard Visual Studio built
>     GDAL DLL (which was much discussed some time ago here and is now
>     available from Tamas' site) in a MinGW environment?
>
>     I spent some time a week or two ago on the issue, but I had a hard
>     time, which AFAIK is because the DLL mixes two function export
>     methods and thus using the standard tools seems difficult if not
>     impossible (I already downloaded the sources for latest GNU
>     dlltool and considered hacking it...)
>
>     The best page about the issue I found so far is this:
>     http://wyw.dcweb.cn/stdcall.htm
>
>     Anybody have any ideas? Is my observation about the two export
>     methods correct and why is that?
>
>     Ari
>
>
>     On 01/29/2011 04:59 AM, Frank Warmerdam wrote:
>
>         Folks,
>
>         I have had good success with the GDAL 1.8 upgrade and I have
>         now thrown
>         the switch migrating it into the production version of OSGeo4W.
>
>         I have upgraded "gdal", "gdal-python", "gdal-mrsid" and
>         "gdal-autotest".
>         I have yet to upgrade the ecw, and sde related drivers, and I
>         have not
>         upgraded the java bindings.  I will try to work on them tomorrow.
>
>         The gdal15dll package was created for backward compatability
>         and should
>         be automatically pulled in.  It seems to be working fine for
>         OpenEV.
>
>         I would encourage folks building packages to update, and
>         rebuild them
>         using the current GDAL.  The GDAL include files in
>         C:\OSGeo4W\include
>         and libraries in C:\OSGeo4w\lib should now be for 1.8.
>
>         Note that the new GDAL package is built using Visual Studio 2008
>         Express instead of 2003.  If you are using the C++ API this
>         may cause
>         issues but if you use the C API it should be invisible.
>
>         Let me know of problems.
>
>         Best regards,
>
>
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