[racket-dev] Extflonum type for windows

Great! This all looks like the right idea, and I'll take a closer look
as soon as possible, but maybe not until the end of the week.

At Mon, 4 Mar 2013 19:06:32 +0300, Michael Filonenko wrote:
> Hello all,
> 
> The following pull request provides long double type (extflonum) on
> win32: https://github.com/plt/racket/pull/265
> 
> Extflonum arithmetic is implemented in a set of functions
> compiled into longdouble.dll (dll and lib attached, source
> code included in the pull request). It has been compiled
> with mingw-w64. In ordinary mingw there is no long double
> input (neither non-msvc strtold nor scanf).
> 
> All those functions accept a special long_double union:
> 
> #define SIZEOF_LONGDOUBLE 16
> typedef union long_double
> {
>   char bytes[SIZEOF_LONGDOUBLE];
> #ifdef __MINGW__
>   long double val;
> #endif
> } long_double;
> 
> Racket's libffi uses this union for ffi facilities instead
> of ffi_type_longdouble, because ffi_type_longdouble is
> defined to ffi_type_double on win platforms.
> 
> To compile the longdouble library yourself, use the following
> commands:
> (mingw-w64, msvc environments are required):
> 
> cd src/racket/src/longdouble
> gcc.exe -shared -o longdouble.dll longdouble.c
> -Wl,--output-def,longdouble.def,--out-implib,longdouble.a -I.
> lib /machine:i386 /def:longdouble.def
> copy /Y longdouble.dll ..\..\..\..\lib\.
> 
> It seems that RacketCGC is supposed to be built without any
> third-party DLLs (longdouble.dll being one of them), so the
> following building process seems natural:
> 
> 1. RacketCGC builds with Visual Studio, without MZ_LONG_DOUBLE
> and without longdouble.dll. (There is currently no MS_LONG_DOUBLE
> macro
> in worksp/mzconfig.h)
> 
> 2. RacketCGC is called to download third-party libraries, including
> longdouble.dll and longdouble.lib
> 
> 3. gc2/make.rkt is called to compile Racket3m. It uses command
> line options to define MS_LONG_DOUBLE macro for the compiled
> code and to link it against longdouble.lib
> 
> Matthew, could you please adjust the build scripts so that
> items 2 and 3 work? Or, of course, any other way that you find
> convenient.
> 
> There are some issues which I do not know how to solve, because they
> depend on racket maintainers work style.
> 
> Some miscellaneous notes:
> 
> 1. There is currently a problem with the code generation in
> foreign.rktc.
> As a result of foreign.rktc's code generation, line 1974 is supposed
> to be:
>    tmp = (mz_long_double)(SCHEME_MAYBE_LONG_DBL_VAL(val));
> Unfortunately, that does not compile, saying
>    error C2440: 'type cast' : cannot convert from 'long_double' to
> 'mz_long_double'
> So we must not cast the structure value type into itself.
> Good news is that simple assignment without casting works fine.
> Probably there is a need for an option in foreign.rktc declaratons
> to turn off casting in this partuicular case. Matthew, it is possible
> to add such an option?
> 
> 2. xform.rkt contains a long list of all long double arithmetic
> [non-]functions.
> 
> 3. In numstr.c I could not avoid separating the parsing of
> double and long double values.
> 
> 
> I have tested the code on windows 7 x86 msvc 2008 (virtualbox).
> x64 has not been tested yet.
> 
> Binary longdouble library can be found here:
> https://github.com/filonenko-mikhail/racket/tree/extflonum-windows/src/racket/s
> rc/longdouble
> 
> --
> With best regards, Michael Filonenko