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Solar wrote:

JamesM wrote:

Code: Select all

MyClass::instance().doStuff();

compiles down to the equivalent of:

Code: Select all

MyClass myClass;
myClass.doStuff();

With -O3.

It does? I mean, instance() contains at least a check whether the singleton has been initialized. If you want to be thread-safe, that check would have to be mutexed. I don't say it's impossible to optimize that away, but...

Ah well.

Ah - it doesn't. We don't use a full-on singleton pattern - the singleton pattern is used only so that a variable can be accessed statically from anywhere. The accessor tends to look something like:
Which of course, can be compiled down into nothingness. I understand your point better now, and yes there would normally be an overhead, but we've done away with this at the expense of no init checks.

James