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

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 :

...

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 :

...

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@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