Dll for Pascal, case sensitiviy in inc. file

[Todd Wasson]

Hello,

I'm writing a Dll file that a customer needs for his Pascal
program. I'm fairly new to Dll file creation, and would appreciate
any assistance here. The customer would like to be able to write
his Pascal header/include file in the same standard format he's
accustomed to. There will be several simple functions in the PowerBasic
Dll that look like this:

FUNCTION Set_Array_Value (BYVAL Array_Index AS LONG,BYVAL Value AS SINGLE) EXPORT AS LONG
  Array_Value(Array_Index)= Value
END FUNCTION

Small arrays similar to this will be global to and operated on mostly from
within my Dll, as this is for a high speed physical simulation and it's
necessary to avoid as many function calls on his end as possible. Currently,
his Pascal declaration for a function like this appears as:

function SET_ARRAY_VALUE(Array_Index: Integer; Value: Single): integer; stdcall; external 'The.dll';

However, since a capitalized function declaration is unusual in his
work, he would like to declare it as follows:

function Set_Array_Value(Array_Index: Integer; Value: Single): integer; stdcall; external 'The.dll';

The PowerBasic test version of the declaration (.Inc file) works fine and
looks like:

DECLARE FUNCTION Set_Array_Value LIB "THE.DLL" 
(BYVAL Array_Index AS LONG, BYVAL Value AS SINGLE) AS LONG

He suggested changing the function itself inside my DLL to include an
ALIAS as follows:

FUNCTION Set_Array_Value ALIAS "Set_Array_Value" (BYVAL Array_Index AS LONG,BYVAL Value AS SINGLE) EXPORT AS LONG
  Array_Value(Array_Index)= Value
END FUNCTION

He hoped that the above change to my Dll function would enable
him to use mixed/lowercase letters in his Pascal declaration, i.e.:

function Set_Array_Value(Array_Index: Integer; Value: Single): integer; stdcall; external 'the.dll';

However, when changing the Dll function to include the ALIAS, the
function does not appear to get called at all by my PowerBasic EXE test
program. If it is possible, how can I change the Dll function itself to
allow him to use the mixed case (Set_Array_Value) declaration on his end?

Thank you, and I hope you all had a wonderful holiday season and a
great New Year's Eve!!

Todd Wasson
Performance Simulations
Drag Racing and Top Speed
Prediction Software http://PerformanceSimulations.Com

P.S. I just tried the following Dll change and it worked through the PowerBasic test
EXE:

FUNCTION Set_Array_Value ALIAS "SET_ARRAY_VALUE" (BYVAL Array_Index AS LONG,BYVAL Value AS SINGLE) EXPORT AS LONG
  Array_Value(Array_Index)= Value
END FUNCTION

It seems that setting an ALIAS that exactly matches the function
name itself is pointless, and does not work. Would the customer's
following Pascal declaration work with the above Dll change?

function Set_Array_Value(Array_Index: Integer; Value: Single): integer; stdcall; external 'the.dll';

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[This message has been edited by Todd Wasson (edited December 31, 2000).]

[Semen Matusovski]

If in DLL FUNCTION Set_Array_Value ALIAS "Set_Array_Value" (BYVAL Array_Index AS LONG,BYVAL Value AS SINGLE) EXPORT AS LONG
in Exe should be DECLARE FUNCTION Set_Array_Value LIB "THE.DLL" ALIAS "Set_Array_Value" (BYVAL Array_Index AS LONG, BYVAL Value AS SINGLE) AS LONG

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E-MAIL: [email protected]

[Todd Wasson]

Semen,
Thank you for your quick reply. I tried this, but now, the function
does not appear to get called at all. Placing a MSGBOX inside the Dll
function resulted in nothing. Perhaps I am making a mistake somewhere else?

In EXE/INC.:

DECLARE FUNCTION Set_Array_Value LIB "THE.DLL" ALIAS "Set_Array_Value" (BYVAL Array_Index AS LONG, BYVAL Array_Value AS SINGLE) AS LONG
''Calling the function itself
Set_Array_Value 1,10.3

In DLL:

FUNCTION Set_Array_Value ALIAS "Set_Array_Value" (BYVAL Array_Index AS LONG, BYVAL Array_Value AS SINGLE) EXPORT AS LONG
 Array_Stored_Value(Array_Index) = Array_Value
 MSGBOX STR$(Array_Stored_Value(Array_Index))
END FUNCTION

I'm stumped here. Where else could I be making a mistake?
Thanks,
Todd


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[Semen Matusovski]

Todd --
This works fine on my PC

Exe:

   #Compile Exe
   Declare Function Set_Array_Value Lib "THE.DLL" Alias "Set_Array_Value" (ByVal Array_Index As Long, ByVal Array_Value As Single) As Long
   Function PbMain
      Set_Array_Value 1, 10.3
   End Function

Dll:

  #Compile Dll "THE.DLL"
  Function Set_Array_Value Alias "Set_Array_Value" (ByVal Array_Index As Long, ByVal Array_Value As Single) Export As Long
     Dim Array_Stored_Value(10) As Global Single
     Array_Stored_Value(Array_Index) = Array_Value
     MsgBox Str$(Array_Stored_Value(Array_Index))
  End Function

Because in DLL you use an array Array_Stored_Value, I added it's declaration.






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E-MAIL: [email protected]

[Todd Wasson]

Thank you, Semen. As usual, you are correct! I had made the mistake
of using an incorrect #INCLUDE in my test EXE, which was referencing
an out of date file. By placing the DECLARE FUNCTION line in the EXE
itself, the code worked immediately. By changing the #INCLUDE line to
access the CORRECT file with your declaration, it worked.

Thanks again,
Todd

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[Scott Turchin]

I was just peruzing through this and curious myself, as a refresher...

I understand PowerBasic exports all uppercase, is that correct?

Except that PB EXE's can see the functions, whereas C or pascal or whatnot cannot unless they call all uppercase???


SO hence an Alias statement is added to give the mixed case for other compilers?


Thanks,

Scott

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Scott
mailto:[email protected][email protected]</A>

[John Kovacich]

Scott,
I think the key is that PB defaults to uppercase, and an alias
is used to override that default. When PB calls a PB DLL, if neither
use an alias, they both use upper case and there is no problem. If
the DLL uses an alias, though, the calling pgm must use a matching alias
to override its upper case default.



------------------
Thanks,

John Kovacich

[Lance Edmonds]

Internally, the compiler capitalizes all variable and sub/function names during the compilation process to ensure the compiler is case-insensitive to things like "MyVariable&" and "myvariable&", etc. By default, all exported and imported subs/functions are expected to be capitalized unless an explicit ALIAS clause is added to the appropriate prototype (sub/function definition) or DECLARE statement. Therefore, the ALIAS clause is provided to provide compatibility with other languages that may use mixed-case.

Win32 (unlike Win16) is case-sensitive to exported/imported names, so ALIAS's often necessary to ensure that the target sub/function of an external module can be found by Windows during linking.

However, if you are writing your own DLL's for use with PowerBASIC, the use of ALIAS is essentially optional, since PB is consistent with it's capitalization of export and import sub/function names. That is, if you do not use ALIAS anywhere in your code, PowerBASIC and Windows will be able to resolve the target name successfully because everything will be capilatized.

Clear as mud?


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Scott Turchin]

NOpe, clear as glass! That's about what Jim Hugeley told me (Jim where are you??)...


And that makes sense, the part I did not understand was the import part, so if PB capitializes that too, life's great.
I've never used the Alias but one time when a customer was using Boar land (Borland) to do his project....




Scott


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Scott
mailto:[email protected][email protected]</A>