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varOleStr

varOleStr = 8

Example​

function IsAutomationString(const Value: Variant): Boolean;
begin
  Result := (VarType(Value) and varTypeMask) = varOleStr;
end;

Usage​

varOleStr identifies a BSTR-backed Unicode Variant string used for OLE Automation and fixed-type Variant string arrays.

Additional Technical Info​

varOleStr is the base TVarType code $0008 for an OLE BSTR/Delphi WideString. It is a length-prefixed Unicode string allocated and released with Automation-compatible ownership rules.

Use this element type for Automation-compatible Variant string arrays; Delphi's VarArrayCreate rejects Pascal-managed varString and varUString element types. Converting between them can allocate and copy data.

String boundaries

  • BSTR can contain embedded null characters because it carries a length. Native APIs that treat text as null-terminated can truncate it.
  • Conversion from varString decodes an ANSI/RawByteString using its code-page context; unrepresentable or incorrectly tagged bytes can become different Unicode text.
  • A BSTR is text, not an encoded byte buffer. Use varArray or varByte for opaque binary data.
  • A by-reference BSTR borrows external storage and has a stricter lifetime than an owned value.

VarAsType with varOleStr formats/converts the source and can invoke locale-sensitive rules or raise. VarType only inspects the tag; mask away flags when classifying.

The example is source-reviewed only; no BSTR was allocated or converted.

External references

Created 2026-07-15