update(libsinsp): get_dynamic_field constness #2511
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Signed-off-by: Angelo Puglisi <[email protected]>
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Codecov ReportAll modified and coverable lines are covered by tests ✅
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## master #2511 +/- ##
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Coverage 78.35% 78.35%
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Files 281 281
Lines 31689 31689
Branches 4643 4643
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+ Hits 24830 24831 +1
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/milestone 0.22.0 |
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| std::vector<void*> m_fields; | ||
| mutable std::vector<void*> m_fields; |
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What's the reason behind this mutable here?
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We return a pointer to an item inside m_fields, but if the vector is too small, we resize it first (see _access_dynamic_field() above)
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get_dynamic_field calls _access_dynamic_field.
Dynamic fields are lazily constructed there, and inserted into m_fields.
Without the mutable we can't make the thing const.
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What about providing a separate const accessor to the field? In general, I would avoid using mutable as I think it is just a way of hiding non-constness.
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That won't work, unless we make the field loading non-lazy, and I assume it was done like that on purpose (performance reasons? avoiding allocations until the field gets accessed?).
If you think of it as an internal cache, we're not really breaking the "OOP" constness of the class.
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Can we e.g. return nullptr from the const accessor (and handle it in a higher layer by returning the default value)?
This would make it even lazier, if anything (the field would get allocated on write, not on read). I have a vague uneasy feeling about mutable (something something thread safety), but if the nullptr approach doesn't work for whatever reason, I guess this is the way to go
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/milestone 0.23.0 |
What type of PR is this?
Any specific area of the project related to this PR?
/area libsinsp
Does this PR require a change in the driver versions?
What this PR does / why we need it:
Have get_dynamic_field being const, so it can be used as a regular getter.
Which issue(s) this PR fixes:
Fixes #
Special notes for your reviewer:
Does this PR introduce a user-facing change?: