On 22/07/2010 11:50, Michael Van Canneyt wrote:
On Thu, 22 Jul 2010, Jonas Maebe wrote:
On 22 Jul 2010, at 12:06, Martin wrote:
On 22/07/2010 09:57, Sergei Gorelkin wrote:
This is by design. 'const' modifier on ansistring and other
'managed' type arguments instucts the compiler to omit refcount
changes, yielding a faster code. At the same time it prohibits
direct modification to the argument, but nothing can be done if you
modify another location that aliases the argument.
If you need proper refcounting, you should pass the argument by
value (i.e. without 'const' modifier).
So, no need to report as bug then?
Indeed, Sergei is correct. In a language like Pascal, there is no way
for
the compiler to ensure that the constness of parameters is completely
observed. It's more like a hint of the programmer to the code generator
("the values passed to this parameter will not changed, so you can
optimize however you like based on that assumption") than a semantic
condition for the compiler to guarantee ("make sure that I do not change
values passed to this parameter in any way").
For what it is worth: Delphi behaves the same as FPC.
I saw the error in my thinking, after Jonas (re-) explained the meaning
of "const".
and I guess it applies to other types to (as long as they are passed by
reference): e.g records are likely to see changes too...
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