Why you need to make your string parameter a const

I have often wanted to point this out, but didn't really feel the need to, until today, when I was debugging into the RTL.

When you have a string parameter, the compiler makes a call to the RTL routine _UStrAddRef, and _UStrClr.
When you have multiple string parameters, the compiler makes a call for each string parameter to _UStrAddRef, and one call to _UStrArrayClr. In addition, the compiler will compile code similar to a try finally sequence as well.

If you do not make any changes to the string parameter, it is better to make that string parameter a const.

So, assuming you have the following code pattern:

procedure AName(param1: string)

changing it to:

procedure AName(const param1: string)

reduces the 2 calls generated by the compiler.

Here's the disassembly for the procedure X(S1, S2: string)

and here's the disassembly for Y(const S1, S2: string):

As you can see, without the const, the generated code is more verbose.