[fpc-devel] Minor doc error about "const param"
Michael Van Canneyt
michael at freepascal.org
Mon Dec 20 20:31:59 CET 2021
On Mon, 20 Dec 2021, Martin Frb via fpc-devel wrote:
> 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....
Well, that's what I meant with really dirty tricks.
I will probably have to rephrase the documentation to
'The compiler will not allow you to modify the parameter value by assigning something directly to it."
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