string := const : why different implementation for local and result?

Question

In Delphi function result is frequently implemented as var-parameter (not out-parameter despite QC ticket).

String constants are basically variables with negative re

Answer 1

After discussion with David Heffernan, i am starting to think that Delphi compiler just does not know what is the value it assigns to variable. Kind of "type erasure" having place. It cannot tell global constant from local on-stack variable and local string expression. It cannot tell if the source would exist after function exit happened. while we know that is string literal or global constant or anything with lifetime independent of the function execution - the compiler just loses that info. And instead it plays defensive and always cloning the value - just for the chance that it would cease to exist. I am not sure, but that looks reasonable. Though the consequences of this rough indiscriminate codegen rule are one more gotcha in Delphi :-(