Указатель на вариантный тип
Consider the following (simplified code):
function CreateVariantPtr(_Value: variant): pVariant;
begin
GetMem(Result, SizeOf(Variant));
Result^ := _Value;
end;
Seems pretty simple, doesn''t it? Anybody who can spot the bug? I got spurious access violations in the line Result^ := _Value; Ok, the reason: Memory allocated with GetMem is not initialised, so the "Variant" pointed to by Result contains some random data, for example something that might represent a variant type which requires some finalisation when the variant is changed, lets say a variant array of some sort. But this finalisation won''t work because the content is just some random garbage, and sometimes I was lucky (I mean that!) and got an access violation that allowed me to spot the error. The fix:
function CreateVariantPtr(_Value: variant): pVariant;
begin
GetMem(Result, SizeOf(Variant));
Initialize(Result^);
Result^ := _Value;
end;
Взято с сайта: https://www.swissdelphicenter.ch