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C++: Memory Layout and Compiler Directives
godbolt.org/z/ox1aWEr16
Same struct. Three layouts. Wildly different sizes.
default → 8 bytes. packed → 5. alignas(16) → 16.
Where it matters:
- Network Protocols: Use packed structs for a minimal "wire format" to avoid sending wasted padding bytes.
- Hardware Interfaces: Use specific alignments for memory-mapped I/O where hardware expects data at particular boundaries.
- Performance Optimization: Use aligned access for vectorization (SIMD) to enable faster data processing.
- Cross-Platform Compatibility: Ensure a consistent memory layout when compiling code across different architectures.
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