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From the docs: https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/clock?view=msvc-170 > Given enough time, the value returned by `clock` can exceed the > maximum positive value of `clock_t`. When the process has run > longer, the value returned by `clock` is always `(clock_t)(-1)`, as > specified by the ISO C99 standard (7.23.2.1) and ISO C11 > standard (7.27.2.1). Microsoft implements `clock_t` as a `long`, a > signed 32-bit integer, and the `CLOCKS_PER_SEC` macro is defined as > 1000. This macro gives a maximum `clock` function return value of > 2147483.647 seconds, or about 24.8 days. Don't rely on the value > returned by `clock` in processes that have run for longer than this > amount of time.
Sys.times now returns -1 if POSIX clock or times fail on overflow. Unix.times now raises on Unix (it would raise only on Windows). times: https://pubs.opengroup.org/onlinepubs/9799919799/functions/times.html clock: https://pubs.opengroup.org/onlinepubs/9799919799/functions/clock.html
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caml_win32_clock can only run for 24.8 days before overflowing. If we use a uint64_t accounting for 100-nsec intervals, and convert to double (where the maximum integer value is 2**53), the function will report accurate running times for over 28 years.
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Fix
caml_win32_clockoverflowing if wall-clock exceeds 24.8 daysFrom the docs:
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/clock?view=msvc-170
Make
Sys.timereturn -1 on error instead of undefined value