> once the string runs over the GC default (I think 1 GB),

Not wishing to sound snarky, but is there even a valid use-case for concatenating GB+ quantities of strings (or even hundreds of MB) ?

I mean surely you'll (potentially) run into memory exhaustion issues and other fun things ?

Of course there is. 1 GB is not even that big these days.

> Of course there is

When? Why not use ropes and avoid the copy?

personally I don't see a need for it, but I'm sure someone will do something dumb that requires it

While not Go, in C# you can avoid a ton of heap allocations by using StringBuilder instead of concatenation, and the crossover point for one being more efficient than the other is at something like 4 concatenations. But people will always say nonsense about "premature optimization" the moment you care about performance.

In regards to Go, in most cases its a pointless optimization. Unless the string is quite large, its the same result. Go is nothing like C# in this case.

In python since 2.5 (and im sure other languages implemntations) the compiler/implementation recognize this += use case and implement it as a fast one.