[fpc-pascal] reference-counted function results not initialized to nil
dle3ab at angelbase.com
Sat Jun 25 08:31:06 CEST 2016
On 06/24/2016 08:19 PM, Michalis Kamburelis wrote:
>> After upgrading fpc 2.6.4 -> 3.0.0, I'm seeing a bug where (as noted in
>> subject) reference-counted function results are not being initialized to
> They were never guaranteed to be initialized to nil.
> Reference-counted types (unlike other types) cannot contain memory
> garbage. But it doesn't mean that they are always initialized empty
> when the function starts. You need to explicitly do Result := '' if
> your code reads the Result later.
> See similar questions for Delphi:
I never dreamed that
local_var := some_function (param);
can result in the old value of local_var being used inside
some_function. That's what's happening here. I fully expected the result
dynamic array (embedded in a record type) to be initialized to nil, and
have never taken care to initialize dynamic arrays and ansistrings. I'm
astonished that this didn't bite me sooner, actually. Perhaps it is a
culprit in occasional crashes.
I can't see any mention of this in the documentation:
> Luckily, FPC warns about it, at least in my simple test:
it also warns me in a simple test, but it doesn't give any warning in my
Is there any compiler option that I can use to force nil initialization
of ref-counted function results?
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