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D - Difference of Windows/Pascal calling conventions ?

reply Achilleas Margaritis <Achilleas_member pathlink.com> writes:
According to Microsoft documentation, WINAPI is FAR PASCAL and PASCAL is
_pascal. But _pascal is obsolete, and it means __stdcall. So, it seems that for
D, extern(Windows) and extern(Pascal) is the same. Is there any difference ? Is
Pascal really needed ?
Apr 22 2004
next sibling parent Stewart Gordon <smjg_1998 yahoo.com> writes:
Achilleas Margaritis wrote:


 According to Microsoft documentation, WINAPI is FAR PASCAL and PASCAL is
 _pascal. But _pascal is obsolete, and it means __stdcall. So, it seems that for
 D, extern(Windows) and extern(Pascal) is the same. Is there any difference ? Is
 Pascal really needed ?


In that case, extern(Windows) is syntactic sugar for extern(Pascal) 
rather than the other way round.  So it makes more sense to ask if 
Windows is really needed.

I'd leave them both in.  That way, you can make it clear which you're 
interfacing - Pascal code or Windows API.

Stewart.

-- 
My e-mail is valid but not my primary mailbox, aside from its being the 
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Apr 22 2004
prev sibling parent reply "Walter" <walter digitalmars.com> writes:
"Achilleas Margaritis" <Achilleas_member pathlink.com> wrote in message
news:c68c6f$1vsp$1 digitaldaemon.com...

 According to Microsoft documentation, WINAPI is FAR PASCAL and PASCAL is
 _pascal. But _pascal is obsolete, and it means __stdcall. So, it seems


that for

 D, extern(Windows) and extern(Pascal) is the same. Is there any difference


? Is

 Pascal really needed ?


They are different, both in name mangling and in calling convention, and
both are needed because C code on Win32 uses both.
Apr 22 2004
parent reply Achilleas Margaritis <axilmar b-online.gr> writes:
Walter wrote:


 "Achilleas Margaritis" <Achilleas_member pathlink.com> wrote in message
 news:c68c6f$1vsp$1 digitaldaemon.com...
 

According to Microsoft documentation, WINAPI is FAR PASCAL and PASCAL is
_pascal. But _pascal is obsolete, and it means __stdcall. So, it seems


 
 that for
 

D, extern(Windows) and extern(Pascal) is the same. Is there any difference


 
 ? Is
 

Pascal really needed ?


 
 
 They are different, both in name mangling and in calling convention, and
 both are needed because C code on Win32 uses both.
 
 


Excuse me if I insist, but here is a piece from MSDN:


/////////////////////////////////////////////////////////////////////////////////

Obsolete Calling Conventions

Home |  Overview |  How Do I

The __pascal, __fortran, and __syscall calling conventions are no longer 
supported. You can emulate their functionality by using one of the supported 
calling conventions and appropriate linker options.

WINDOWS.H now supports the WINAPI macro, which translates to the appropriate 
calling convention for the target. Use WINAPI where you previously used PASCAL 
or __far __pascal.


/////////////////////////////////////////////////////////////////////////////////

Here is the piece about __stdcall:

/////////////////////////////////////////////////////////////////////////////////

__stdcall

Home |  Overview |  How Do I

Microsoft Specific —>

The __stdcall calling convention is used to call Win32 API functions. The
callee 
cleans the stack, so the compiler makes vararg functions __cdecl. Functions
that 
use this calling convention require a function prototype. The following list 
shows the implementation of this calling convention.
Element 	Implementation
Argument-passing order 	Right to left.
Argument-passing convention 	By value, unless a pointer or reference type is
passed.
Stack-maintenance responsibility 	Called function pops its own arguments from 
the stack.
Name-decoration convention 	An underscore (_) is prefixed to the name. The name 
is followed by the at sign ( ) followed by the number of bytes (in decimal) in 
the argument list. Therefore, the function declared as int func( int a, double
b 
) is decorated as follows: _func 12
Case-translation convention 	None

The /Gz compiler option specifies __stdcall for all functions not explicitly 
declared with a different calling convention.

Functions declared using the __stdcall modifier return values the same way as 
functions declared using __cdecl.

END Microsoft Specific
Example

In the following example, use of __stdcall results in all WINAPI function types 
being handled as a standard call:

// Example of the __stdcall keyword
#define WINAPI __stdcall

/////////////////////////////////////////////////////////////////////////////////

The first piece from MSDN says that _pascal is obsolete.

The second piece says that WINAPI = _stdcall.


The following table shows the Microsoft calling conventions:

http://www.cs.cornell.edu/courses/cs412/2001sp/resources/microsoft-calling-conventions.html

It seems that _pascal is really obsolete.

Of course, Walter, you are much more experienced, so I believe you, but why
does 
Microsoft say that _pascal is obsolete ?
Apr 22 2004
parent "Walter" <walter digitalmars.com> writes:
"Achilleas Margaritis" <axilmar b-online.gr> wrote in message
news:c69d0m$klo$1 digitaldaemon.com...

 Of course, Walter, you are much more experienced, so I believe you, but


why does

 Microsoft say that _pascal is obsolete ?


I wouldn't use it in any new code. But existing legacy C code uses it, and
so it must be supported.
Apr 22 2004