[fpc-devel] Minor doc error about "const param"
lazarus at mfriebe.de
Mon Dec 20 13:11:26 CET 2021
On 20/12/2021 12:29, Michael Van Canneyt wrote:
> On Mon, 20 Dec 2021, Martin Frb via fpc-devel wrote:
>> Actually an commission, but an important one.
>> > Specifying a parameter as Constant is giving the compiler a hint
>> that the contents of the parameter will not be changed by the called
>> "by the called routine."
>> Should that not be "by any code (the caller, the called, or any
>> nested callee, or any other thread, interrupt or hardware modifying
> If the value is copied then nothing else can change it since it is only
> accessible to the routine itself ? (unless you're doing some really dirty
> tricks, obviously)
In the below example "GlobalTxt := 'abc';" is indeed in the "called
But insert a call to a subroutine doing the work, or start a thread....
procedure foo(const t: AnsiString);
GlobalTxt := 'abc';
// do some mem alloc/dealloc work
// do something with t, it still points to the location that the old
content was in. If that mem has been changed....
GlobalTxt := getRandomTextWichIsNotAConstant;
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