On reddit, u/tgolyi reports:
std::format is very cool, but why did you include <format> to <chrono>? This change alone slowed down compilation for our project by 20%. Is it required by the standard now to include <format> (to support std::formatter specialization)? It's just that <chrono> is included by so many other headers like <mutex> and <thread> and Qt too.
Separately from any throughput improvements for <format>, I believe it should be possible to remove this dependency:
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#ifdef __cpp_lib_format
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#include <format>
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#include <iomanip>
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#endif // defined(__cpp_lib_format)
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The fix would presumably involve some combination of:
- Forward declarations (of
formatter etc.)
- Extracting common machinery to a centralized header somewhere (used sparingly, since this costs throughput)
- Possibly templatizing stuff so that it isn't instantiated until needed (need to follow the Standard's lookup rules)
Related to DevCom-10046069 "Including chrono and compiling with -std:c++20 is ten time slower than before" and internal VSO-1543202 / AB#1543202 .
On reddit, u/tgolyi reports:
Separately from any throughput improvements for
<format>, I believe it should be possible to remove this dependency:STL/stl/inc/chrono
Lines 37 to 40 in 4c862ee
The fix would presumably involve some combination of:
formatteretc.)Related to DevCom-10046069 "Including chrono and compiling with -std:c++20 is ten time slower than before" and internal VSO-1543202 / AB#1543202 .