Class Layout
summary
Shows concrete rules and experiments: use offsetof and compiler dumps (GCC/clang/MSVC flags, Godbolt) to see real offsets; C++11 loosens block ordering and C++23 mandates declaration order; apply no_unique_address or rely on EBCO to collapse empty members; composition can make an object 12 bytes versus 8 bytes — a 50% size difference — and microbenchmarks (Google Benchmark, 100 iterations, sizes 100..1e6) find layout-dependent timing with spikes and sometimes up to 4x speed differences for accumulate while results remain platform dependent and inconclusive.
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chapters (11)
- 0:00Introduction
- 1:48Class layout in C++
- 3:35C++ standard layout rules
- 10:27Subobjects and layout
- 13:18Alignment requirements
- 17:01Inheritance vs composition
- 23:05Empty base class optimization
- 27:01Standard layout types
- 31:38Inspecting layout with compiler flags
- 39:17Performance impact of layout
- 49:00Q&A
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