[fpc-devel] Looking for clarification on what I think are obviously missing "const" prefixes for parameters in the methods of TRect (the typshrdh.inc one)

[Walter Prins]

On Sun, 27 Jan 2019 at 01:53, John Doe <slightlyoutofphase at gmail.com> wrote:

> On Sat, Jan 26, 2019 at 7:44 PM Sven Barth via fpc-devel <
> fpc-devel at lists.freepascal.org> wrote:
>
>> Changing this behavior would not only be a backwards incompatibility, but
>> would also violate the ABI which describes how records shall be passed.
>>
>
> On second thought, I definitely agree with you that changing the basic
> behavior of the compiler in that regard sounds like an idea that is not
> remotely possible due to how it would very likely break large amounts of
> existing code. That was a dumb suggestion on my part.
>

Just thinking out loud (probably a bad idea) but:

Would it perhaps be possible to treat this as a type of optimization
however?  Which is to say, if the called routine makes no changes to the
passed record, then it should not matter whether compiler implicitly const
passes the parameter or copies it?  (If the routine *does* change the
passed record then it does the normal thing.)  Of course I have no idea
whether the dataflow analysis I imagine needed to support this is
whatsoever plausible to be done without unacceptable compromises  (And even
then, I'd guess it's not something there'd be sufficient appetite for even
if in theory it might be possible...?)
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