[libcxx-commits] [PATCH] D134742: [libc++][chrono] Implements formatter duration.

[Eric Fiselier via Phabricator via libcxx-commits]

EricWF reopened this revision.
EricWF added a comment.
This revision is now accepted and ready to land.

Please fix the undefined behavior mentioned above.



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Comment at: libcxx/include/__chrono/convert_to_tm.h:43
+    //   day elapsed since midnight.
+    uint64_t __sec = chrono::duration_cast<chrono::seconds>(__value).count();
+    __sec %= 24 * 3600;
----------------
Does this not overflow for a lot of things?

Like `hours(duration_cast<hours>(seconds::max()) + hours(1))`?

Instead of reverting to raw arithmetic on ints, use chrono to get the values you want.

See https://godbolt.org/z/GYc7Tzn9W



Repository:
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https://reviews.llvm.org/D134742