为什么将NIL数组赋给Variant会导致在Delphi 6中返回非空数组？

首先在Variants.DynArrayVariantBounds中.当动态数组为零时,这会错误地返回(0,0)的低/高边界对.它应该返回(0,-1).最新版本的Delphi中修复了此错误.这导致V：= sa返回带有单个空元素的变量数组.

第二个错误影响另一个方向,sa：= V.这个错误仍然存??在于最新版本的Delphi中.这个bug出现在Variants.DynArrayFromVariant中.有一个repeat / until循环遍历输入变量数组并填充输出动态数组.当输入变量数组为空时,它不应该输入repeat / until循环.但是,代码错误地这样做并尝试使用VarArrayGet读取变量数组的元素.由于数组为空,因此会引发运行时错误.我报告了这个：QC#109445.

这是修复错误的一小段代码.请注意,我只考虑数组是一维的情况.如果您需要支持更高维度的数组,那么您可以扩展此方法.

program Project1;

{$APPTYPE CONSOLE}

uses
  Variants;

var
  OriginalVarFromDynArray: procedure(var V: Variant; const DynArray: Pointer; TypeInfo: Pointer);
  OriginalVarToDynArray: procedure(var DynArray: Pointer; const V: Variant; TypeInfo: Pointer);

function DynArrayVarType(typeInfo: PDynArrayTypeInfo): Integer;
const
  tkDynArray  = 17;
begin
  Result := varNull;
  if (typeInfo<>nil) and (typeInfo.Kind=tkDynArray) then
  begin
    Inc(PChar(typeInfo),Length(typeInfo.name));
    Result := typeInfo.varType;
    if Result=$48 then
      Result := varString;
  end;
  if (Result<=varNull) or (Result=$000E) or (Result=$000F) or ((Result>varInt64) and not (Result=varString)) then
    VarCastError;
end;

procedure VarFromDynArray(var V: Variant; const DynArray: Pointer; TypeInfo: Pointer);
var
  VarType,DynDim: Integer;
begin
  DynDim := DynarrayDim(PDynArrayTypeInfo(TypeInfo));
  if DynDim=1 then
  begin
    //only attempt to deal with 1 dimensional arrays
    if DynArray=nil then begin
      VarClear(V);
      VarType := DynArrayVarType(PDynArrayTypeInfo(TypeInfo));
      if VarType = varString then
        VarType := varOleStr;
      V := VarArrayCreate([0,-1],VarType);
      exit;
    end;
  end;
  OriginalVarFromDynArray(V,DynArray,TypeInfo);
end;

procedure VarToDynArray(var DynArray: Pointer; const V: Variant; TypeInfo: Pointer);
var
  DimCount: Integer;
  Len: Integer;
begin
  DimCount:= VarArrayDimCount(V);
  if DimCount=1 then
  begin
    //only attempt to deal with 1 dimensional arrays
    Len := VarArrayHighBound(V,1) - VarArrayLowBound(V,1) + 1;
    if Len=0 then begin
      DynArraySetLength(DynArray,PDynArrayTypeInfo(TypeInfo),1,@Len);
      exit;
    end;
  end;
  OriginalVarToDynArray(DynArray,V,TypeInfo);
end;

procedure FixVariants;
var
  VarMgr: TVariantManager;
begin
  GetVariantManager(VarMgr);
  OriginalVarFromDynArray := VarMgr.VarFromDynArray;
  VarMgr.VarFromDynArray := VarFromDynArray;
  OriginalVarToDynArray := VarMgr.VarToDynArray;
  VarMgr.VarToDynArray := VarToDynArray;
  SetVariantManager(VarMgr);
end;

type
  TDynamicStringArray = array of string;

var
  V: Variant;
  sa: TDynamicStringArray;
begin
  FixVariants;

  sa := nil;
  V := sa;
  sa := V;

  Writeln(Length(sa));
  Readln;
end.