BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  DLL function calls in Excel          BorlandTalk.com Forum Index -> Delphi OLE Automation View previous topic :: View next topic   Author Message A.Afonso Guest Posted: Thu Dec 30, 2004 3:10 pm    Post subject: DLL function calls in Excel Hi everybody, I'm trying to connect from Excel to a funcion declared in a DLL (made in delphi code). I have no problems when using integer or double types. But using concat strings I'm desperate. Simplifying the process, I've defined in Delphi a function like this (inside a MyDll.dll): function ShowText(Text: PChar): PChar; export; stdcall; begin Result := PChar('My text ' + Text); end; And I've defined a macro in VBA in Excel like this: Declare Function VBShowText Lib "MyDll.dll" Alias "ShowText" (ByVal a As String) As String If I include in a cell the call: =VBShowText(A1), the cell shows always rubbish (some chinesse symbols I think...). I've tried a lot of combinations of PChar, array of Char, string, Concat, StrPCopy, etc. Same or worst results. Note: The function works ok from an exe Delphi program. Also works ok if it is called from an exe VS C# program. Another Note: If I substitute Result := PChar('My text ' + Text); by Result := Text; everything is ok. The problem is when I concat the strings. Thanks in advance, Augusto. Back to top Avatar Zondertau Guest Posted: Thu Dec 30, 2004 3:35 pm    Post subject: Re: DLL function calls in Excel Quote: I'm trying to connect from Excel to a funcion declared in a DLL (made in delphi code). I have no problems when using integer or double types. But using concat strings I'm desperate. Simplifying the process, I've defined in Delphi a function like this (inside a MyDll.dll): function ShowText(Text: PChar): PChar; export; stdcall; begin Result := PChar('My text ' + Text); end; And I've defined a macro in VBA in Excel like this: Declare Function VBShowText Lib "MyDll.dll" Alias "ShowText" (ByVal a As String) As String If I include in a cell the call: =VBShowText(A1), the cell shows always rubbish (some chinesse symbols I think...). I've tried a lot of combinations of PChar, array of Char, string, Concat, StrPCopy, etc. Same or worst results. Ouch! Looking at this code hurts my eyes! This is not because of the bug you're referring to. This is probably because to my knowledge Visual Basic uses Unicode strings instead of Ansi strings. That would probably be solved by replacing each string-related type (string, PChar, Char) by it's Unicode equivalent (WideString, PWideChar, WideChar). A major problem with your code is, however, the way you're mixing strings and PChars. The code you're using may result in memory leaks or random access violations. Rudy Velhuis' article will explain the trouble you'll run into when mixing Delphi strings and PChars: http://rvelthuis.bei.t-online.de/articles/articles-pchars.htm Unfortunately I don't know a direct approach for solving this bug. In any case returning a PChar should be avoided. Generally the caller should allocate a buffer, pass it and it's length to the callee and then the callee should write it's result to that buffer. I don't know if Excel is capable of doing this. Back to top George Birbilis Guest Posted: Thu Dec 30, 2004 5:19 pm    Post subject: Re: DLL function calls in Excel try PAnsiChar, not PChar Back to top Avatar Zondertau Guest Posted: Thu Dec 30, 2004 5:24 pm    Post subject: Re: DLL function calls in Excel Quote: try PAnsiChar, not PChar PAnsiChar is the same as PChar. It's PWideChar that should be used instead of PChar. This doesn't solve the other, IMHO worse, problem though. Back to top George Birbilis Guest Posted: Thu Dec 30, 2004 6:35 pm    Post subject: Re: DLL function calls in Excel Quote: If I substitute Result := PChar('My text ' + Text); by Result := Text; everything is ok. The problem is when I concat the strings. * try Result:=PChar('My text' + String(Text)); * else var s:string; .... s:=Text; Result:=PChar('My text'+s); does either of these help? ----- George Birbilis (birbilis (AT) kagi (DOT) com) http://www.kagi.com/birbilis -------------- Back to top A.Afonso Guest Posted: Fri Dec 31, 2004 10:25 am    Post subject: Re: DLL function calls in Excel Many thanks Avatar and George, I've been trying your suggestions. No success at all. Also I read the Rudy Velhuis' article and I've been trying more options. Nothing. I'm considering hardly to rewrite the dll as VBA functions. It is a pitty, because de dll has many functions involved. Thanks again, A.Afonso Back to top willem van Deursen Guest Posted: Fri Dec 31, 2004 3:30 pm    Post subject: Re: DLL function calls in Excel I hope you do know already this article, but otherwise, it might contain some useful information for you, and it allows you to bybass your VBA code, maybe, maybe. http://www.howtodothings.com/showarticle.asp?article=187 Hope this helps Willem A.Afonso wrote: Quote: Many thanks Avatar and George, I've been trying your suggestions. No success at all. Also I read the Rudy Velhuis' article and I've been trying more options. Nothing. I'm considering hardly to rewrite the dll as VBA functions. It is a pitty, because de dll has many functions involved. Thanks again, A.Afonso -- Willem van Deursen, The Netherlands [email]wvandeursen_nospam (AT) nospam_carthago (DOT) nl[/email] replace _nospam@nospam_ for @ to get a valid email address www.carthago.nl Back to top A Pham Guest Posted: Sat Jan 01, 2005 7:45 pm    Post subject: Re: DLL function calls in Excel This code will never work. It is lucky that you get no access violation or garbage. Delphi string is a automatically freed when out of scope or no more reference count. Need to change to codes below and remember to free when receive or allocate enough space and pass it to this function function ShowText(Text: PChar): PChar; export; stdcall; var S: string; begin S := 'My text ' + Text; GetMem(Result, Length(S) + 1); Move(Pointer(S)^, Result^, Length(S)); PChar(Integer(Result) + Length(S))^ := #0; end; Cheers A Pham "A.Afonso" <aafonso (AT) ids-sa (DOT) es> wrote Quote: Hi everybody, I'm trying to connect from Excel to a funcion declared in a DLL (made in delphi code). I have no problems when using integer or double types. But using concat strings I'm desperate. Simplifying the process, I've defined in Delphi a function like this (inside a MyDll.dll): function ShowText(Text: PChar): PChar; export; stdcall; begin Result := PChar('My text ' + Text); end; And I've defined a macro in VBA in Excel like this: Declare Function VBShowText Lib "MyDll.dll" Alias "ShowText" (ByVal a As String) As String If I include in a cell the call: =VBShowText(A1), the cell shows always rubbish (some chinesse symbols I think...). I've tried a lot of combinations of PChar, array of Char, string, Concat, StrPCopy, etc. Same or worst results. Note: The function works ok from an exe Delphi program. Also works ok if it is called from an exe VS C# program. Another Note: If I substitute Result := PChar('My text ' + Text); by Result := Text; everything is ok. The problem is when I concat the strings. Thanks in advance, Augusto. Back to top George Birbilis Guest Posted: Mon Jan 10, 2005 8:40 pm    Post subject: Re: DLL function calls in Excel btw, autogenerated Delphi DLLs (from "File/New" menu) have a comment that says about "Borland Memory Manager DLL". See if that comment gives any help in your case ----- George Birbilis (birbilis (AT) kagi (DOT) com) http://www.kagi.com/birbilis -------------- Quote: This code will never work. It is lucky that you get no access violation or garbage. Delphi string is a automatically freed when out of scope or no more reference count. Need to change to codes below and remember to free when receive or allocate enough space and pass it to this function function ShowText(Text: PChar): PChar; export; stdcall; var S: string; begin S := 'My text ' + Text; GetMem(Result, Length(S) + 1); Move(Pointer(S)^, Result^, Length(S)); PChar(Integer(Result) + Length(S))^ := #0; end; Cheers A Pham "A.Afonso" <aafonso (AT) ids-sa (DOT) es> wrote in message news:41d41967 (AT) newsgroups (DOT) borland.com... Hi everybody, I'm trying to connect from Excel to a funcion declared in a DLL (made in delphi code). I have no problems when using integer or double types. But using concat strings I'm desperate. Simplifying the process, I've defined in Delphi a function like this (inside a MyDll.dll): function ShowText(Text: PChar): PChar; export; stdcall; begin Result := PChar('My text ' + Text); end; And I've defined a macro in VBA in Excel like this: Declare Function VBShowText Lib "MyDll.dll" Alias "ShowText" (ByVal a As String) As String If I include in a cell the call: =VBShowText(A1), the cell shows always rubbish (some chinesse symbols I think...). I've tried a lot of combinations of PChar, array of Char, string, Concat, StrPCopy, etc. Same or worst results. Note: The function works ok from an exe Delphi program. Also works ok if it is called from an exe VS C# program. Another Note: If I substitute Result := PChar('My text ' + Text); by Result := Text; everything is ok. The problem is when I concat the strings. Thanks in advance, Augusto. 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