ITypeInfo.GetIdOfNames definition problem
lazarus / 67-Windows

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440bx · 2025-06-29 06:11

Hello,

In activex.pp, in the ITypeInfo interface, the method GetIdOfNames is
defined as:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i      
Function  GetIDsOfNames(CONST rgszNames: pOleStr; cNames: UINT; OUT
pMemId: MEMBERID):HResult;StdCall; In that definition the first
parameter is a pointer to an OleStr (note that in this case "const"
does not cause a pointer to that pointer to be passed as the first
parameter, IOW, in this case, "const" has no functional effect.)

The C definition of that method is:
Code: C  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i HRESULT
GetIDsOfNames(  [in]  LPOLESTR *rgszNames,  [in]  UINT     cNames, 
[out] MEMBERID *pMemId); The first parameter is a pointer to an array
of pointers to arrays of wide characters.

In Pascal that would be ^^OLESTR or ^POLESTR or PPOLESTR.

The current Pascal definition declares a pointer to a widechar array
instead of a pointer to an array of pointers to widechar arrays.

Note that using "var" or "constref" to a pwidechar in this case does
not declare that it is an array of pointers which complicates matters
if/when the method needs to be used.

HTH.

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gues1 · 2025-06-29 10:02

Quote from: 440bx on June 29, 2025, 08:11:45 amIn activex.pp, in the
ITypeInfo interface, the method GetIdOfNames is defined as:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i      
Function  GetIDsOfNames(CONST rgszNames: pOleStr; cNames: UINT; OUT
pMemId: MEMBERID):HResult;StdCall; 
May be this will be the correct definitiion ?
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i      
Function  GetIDsOfNames(rgszNames: pOleStrLIST; cNames: UINT; OUT
pMemId: MEMBERID):HResult;StdCall;      //pOleStrList is definied in
the head of unit:     POleStrList = ^TOleStrList;     TOleStrList =
array[0..65535] of POleStr;

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440bx · 2025-06-29 10:32

That would work but, it doesn't follow the pattern in existing correct
definitions of arguments that are arrays.

The argument should be a pointer to the first array element.  Pointer
arithmetic automatically makes that pointer be a pointer to any size
array.  This makes the separate declarations of ...LIST unnecessary.

Basically, in C, C++ and FPC, a pointer to a <type> is also a pointer
to an array of <type>.  This often makes the declaration of array
types unnecessary since the pointer implicitly defines an array of
<type>.

for instance, p : ^integer;  makes p not only a pointer to an integer
but also a pointer to an array of integers.

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gues1 · 2025-06-29 13:10

Quote from: 440bx on June 29, 2025, 12:32:28 pmThe argument should be
a pointer to the first array element.  Pointer arithmetic
automatically makes that pointer be a pointer to any size array.  This
makes the separate declarations of ...LIST unnecessary.
Basically, in C, C++ and FPC, a pointer to a <type> is also a pointer
to an array of <type>.  This often makes the declaration of array
types unnecessary since the pointer implicitly defines an array of
<type>.
for instance, p : ^integer;  makes p not only a pointer to an integer
but also a pointer to an array of integers.

This is something I don't like. Not at all.
The fact that you can behave like in C is an absolute plus for
performance, but for stability and possible bugs... I would say we are
definitely not there.
I know of course that it can be done but I think that something like
this should be absolutely avoided (at most I can understand it limited
to RTL or RTTI).