Hello, fin_81, you wrote: _> You did not read wiki under the link which I gave. The approximate plan In the same place it is written "optimize application startup time", about the size it is told nothing! Here looked, I see: When/LTCG is used to link modules compiled by using/Og,/O1,/O2, or/Ox, the following optimizations are performed: Cross-module inlining Interprocedural register allocation (64-bit operating systems only) Custom calling convention (x86 only) Small TLS displacement (x86 only) Stack double alignment (x86 only) Improved memory disambiguation (better interference information for global variables and input parameters) But after all it is all about speed, about file size is told nothing. _> collect Qt: make|gmake|nmake or that under Windows. While gathers qt, you can smoke, have a sleep or go to holiday as carries. It yes, yesterday collected under msvc2015. A question: I so understand, what it is simple the assumption? About the size anywhere it is told nothing, in difference from the same option/OPT:REF where it is explicitly written, and I already upon see.