On Tue, 02 Jun 2009, Szak�ts Viktor wrote:
Hi,
> We still have some non-portable code to support DLL calls on Windows.
> The problem with this is that it only works on x86 Windows systems
> (this means it isn't available on WinCE, x64 and IA64) and the implementation
> uses inline ASM to solve the problem.
> Is it possible to replace DynaCall() function with a portable,
> pure C solution?
AFAIK no but it can be hacked to use pure C code for chosen platforms
if you know well used ABI (calling convention).
F.e. for x64 1-st 10 parameters are passed in registers without touching
stack (AFAIR RAX, RCX, R1, R2, ..., R8). These are 64bit registers so
they can be used to hold most of data types without any casting or dividing
(except long double and some structures). It means that it should be enough
to introduce pseudo function with 10 parameters and cast real function
to this one before calling, f.e. sth like:
typedef LONGLONG ( CALLBACK * _DLL_FUNC_ )
( LONGLONG p1, LONGLONG p2, LONGLONG p3, LONGLONG p4, LONGLONG p5,
LONGLONG p6, LONGLONG p7, LONGLONG p8, LONGLONG p9, LONGLONG p10 );
LONGLONG p[ 10 ], llresult;
_DLL_FUNC_ lpFunc;
/* initalize params casting them to LONGLONG: */
p[ 0 ] = ( LONGLONG ) ...;
p[ 1 ] = ( LONGLONG ) ...;
...
/* initialie function address: */
lpFunc = ( _DLL_FUNC_ ) GetProcAddress;
/* call function */
llresult = (lpFunc)( p[ 0 ], p[ 1 ], p[ 2 ], p[ 3 ], p[ 4 ],
p[ 5 ], p[ 6 ], p[ 7 ], p[ 8 ], p[ 9 ] );
I cannot test it but it should work though it's possible that some
types are not returned in RAX and in such case we will have to introduce
second version of such function declared with different return type.
Similar hacks can be introduced also for other calling conventions
but some of them force strict number of parameters so the caller
has to use casting to 10 different functions depending on number of
passed parameters and some parameters like 64bit integers or double
values should be divided into two ones if parameter holder is not large
enough f.e. on 32 bit systems. Some types may also need special handling
for returned values and repeated function declaration.
AFAIR maximum number of DLL function parameters on x...@32 is 16.
We have two calling conventions C and STD and 3 methods of returning
parameters: LONGLONG, double, float. So finally we will need 16 * 2 * 3
pseudo functions which will be used in pure C code with strict number
of normalized parameters.
Someone who use windows, knows assembler and calling convention used
in this OS should be able to create such code and test it. Current ASM
code can be used as source for parameters conversion and types of functions.
Sorry but due to limited access to this system I cannot make it myself.
It's possible that such code written for x...@32 will also work with
wi...@arm without any modifications or with some small ones in parameter
encoding or additional exceptions for returned values.
best regards,
Przemek
_______________________________________________
Harbour mailing list
[email protected]
http://lists.harbour-project.org/mailman/listinfo/harbour
