Bug report

LogRecord.msecs returns an incorrect value when timestamp (self.ct) value has exactly 100ms.

One liner check:

assertint((1677793338.100_000_0-int(1677793338.100_000_0))*1000)+0.0==100.0

The issue is binary representation of "0.1" / floating point error:

>>># Definition of LogRecord.msecs:>>># https://github.com/python/cpython/blob/12011dd8bafa6867f2b4a8a9e8e54cb0fbf006e4/Lib/logging/__init__.py#L343>>># int((ct - int(ct)) * 1000) + 0.0>>>ct=1677793338.100_000_0>>>ct1677793338.1>>>ct-int(ct)0.09999990463256836>>> _*100099.99990463256836>>>int(_)99>>> _+0.099.0

Your environment

• CPython versions tested on:
  • 3.10.9
  • 3.11.2
• Operating system and architecture:
  • Custom company OS based on Debian Testing
  • 64-bit

Discussion

I think switching totime.time_ns whensetting the creation time might be one solution.

Linked PRs

• gh-102402: Fix floating point math issue by usingtime.time_ns() inlogging.LogRecord #102412
• gh-102402: Fix logging test_relativeCreated_has_higher_precision() leak #117985
• gh-102402: Make test_relativeCreated_has_higher_precision less implementation dependent #118062