Progress Report: Adopting Header Units in Microsoft Word
summary
Microsoft Word adopts C++20 header units via MSVC’s translate include and an IFC map, measuring inner-loop compile times across three machine classes (BTW, physical dev workstation, Microsoft Dev Box) with seven-run benchmarks over three weeks. Results show 1% regression / 21% improvement depending on workload (full build ~6,500 files vs focused folders of ~300 and ~200 files), object sizes grow (sum of objs ~22% larger, median 25%) due to duplicated debug info, and fixes (linker and PDB/IFC reuse) are required to realize consistent gains.
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