Comment by TickleSteve

He's describing unused-function removal... which "-flto" is the correct option to use (on GCC). like you say, without this, removal is only performed within the compilation-unit, but my statement was quite correct.

@majewsky: what you're describing is more akin to "-ffunction-sections" and "-gc-sections" which will split ewach function into a separate section and garbage-collect those sections.