Add escape hatches for source-breaking throughput improvements #3027
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strega-nil-ms
approved these changes
Aug 11, 2022
CaseyCarter
approved these changes
Aug 11, 2022
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Originally,
_SILENCE_STDEXT_HASH_DEPRECATION_WARNINGSwas the escape hatch to allow<hash_map>and<hash_set>to be included. #2996 extended this to restore<xhash>'s inclusion of<cstring>/<cwchar>/<xstring>and defining commonstdextmachinery. However, I attempted to unconditionally remove the non-Standard using-declaration that providedstd::hash_compare. Unfortunately, there are still projects depending on this. 😿 We can preserve the throughput improvement and give affected projects a way out by extending the escape hatch to also provide the using-declaration.Also, #2998 got
<functional>to stop including<memory>in C++17 mode. We're seeing at least one affected project (Qt5) where fixing the source may be difficult. We can add a targeted escape hatch for this inclusion, again preserving the throughput improvement by default.