[ETW] Add configuration to export 64-bit integer as timestamp #3286
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| constexpr int64_t FILETIME_EPOCH_DIFF = 11644473600LL; // Seconds from 1601 to 1970 | ||
| constexpr int64_t HUNDRED_NANOSECONDS_PER_SECOND = 10000000LL; | ||
| int64_t unix_time_seconds = (filetime / HUNDRED_NANOSECONDS_PER_SECOND) - FILETIME_EPOCH_DIFF; | ||
| int64_t unix_time_nanos = unix_time_seconds * 1'000'000'000 + (filetime % HUNDRED_NANOSECONDS_PER_SECOND) * 100; |
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Do we need to check for the overflow, as unix_time_seconds can be large value in uint64_t, and we are multiplying with 1'000'000'000 , followed by addition.
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I am not sure how should overflow be handled here, but it seems it is converted into time64_t which doesn't take the signing of int64_t into account (see here, probably passing overflowed value is fine here, which will just be treated as sort of invalid timestamp and returns some new or old timestamp.
Please feel free to correct me.
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I did some test here - https://godbolt.org/z/dGoen89bh, and can see the overflow happening for the filetime > year 2280. The existing code is used for conversion of the current timestamp (span start time, log timestamp etc), which should be fine as it won't overflow. However, with timestamp coming as attribute can have any value past year 2280, and this can overflow.
This should be fine for now, but good to add some code comment so it can be revisited.
[ETW] Add configuration to export 64-bit integer as timestamp (open-telemetry#3286)
Changes
Add macro
OPENTELEMETRY_ATTRIBUTE_TIMESTAMP_PREVIEWto ETW exporter to support exporting a given 64-bit integer as timestamp type, because timestamp is not supported in the attribute type.For significant contributions please make sure you have completed the following items:
CHANGELOG.mdupdated for non-trivial changes