[Haskell-cafe] Re: building HSQL MySQL on windows (Was: FFI imported function names)

[Simon Marlow]

Daniil Elovkov wrote:
> Ok, enough talking to myself :)
> 
> If anybody ever wants to build hsql-mysql on windows and has the same
> problems as I had, here's how it should be done.
> 
> The problem I had seemed to be that libmysql.dll uses stdcall, but
> names its functions without @<n> decoration. Thus, when linking a
> Haskell program against it, names with @<n> cannot be resolved.
> 
> The solution is pretty much a hack. Somebody from the Ruby community
> used to run into the same problem, from the same situation -- namely
> building ruby mysql bindings.
> 
> Here is the procedure one person suggests
> http://rubydotnetproxy.rubyforge.org/mysql_win.html
> 
> It worked perfectly for me. Of course, with some cabal specifics,
> which is obviously not described in the above page.
> 
> The solution was to create a def file listing the names which could
> not be resolved and creating a .a file based on the dll and this def
> file.

GHC adds the @N suffix to any foreign function declared with the stdcall 
calling convention, which I think matches what gcc does.  I wonder how it 
works for C.

Cheers,
	Simon


> 
> 2008/12/24 Daniil Elovkov <daniil.elovkov at googlemail.com>:
>> Mm, actually I didn't change the calling convention ffi imports when I
>> thought I did. I tried to do it through defines...
>>
>> Well, by explicitly saying ccall I get the names without @<n>
>> decoration. And it all links well. But I get segault when I run the
>> code, which should mean that calling conventions didn't match.
>>
>> Actually I found some ramblings on the internet that there's something
>> wrong with libmysql.dll and libmysql.lib in this respect, but they
>> were from 2004.
>>
>> Thus the question: how do I link against a lib file in ghc? When I say
>> -lmysql on command line it strictly searches for dll and complains if
>> it's not found. Adding lib exlpicitly on the cmd line doesn't seem to
>> have any effect.
>>
>> Thanks
>>
>>
>> 2008/12/24 Daniil Elovkov <daniil.elovkov at googlemail.com>:
>>> Hello
>>>
>>> How is decided whether the name of imported function gets the ending
>>> of the form @4 in ghc?
>>>
>>> I'm having this problem on Windows trying to use HSQL MySQL on windows.
>>>
>>> I compile HSQL Oracle backend and I get names without that. It's ok.
>>> With HSQL MySQL I get names with that stuff. It prevents me from
>>> further linking to dll. Supplying in the ghc command-line the "lib"
>>> file where names have those marks doesn't have any effect.
>>>
>>> The linker says that fname at NN cannot be resolved.
>>>
>>> Can I control that?
>>>
>>> The ffi calling convention doesn't (and shouldn't as I understand)
>>> affect this. The only difference is that in the case of mysql the
>>> header file itself where functions are described marks it STDCALL. Is
>>> that the reason?
>>>
>>> Also I changed ffi import line from "hsmysql.h func" to just "func",
>>> to no avail.
>>>
>>> ghc 6.8.2
>>>
>>> I'm lost. Please help.
>>>
>>> --
>>> Daniil Elovkov
>>>
>>
>>
>> --
>> Daniil Elovkov
>>
> 
> 
>