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Add support for enums with non-default size #17009

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@pcanal pcanal commented Nov 22, 2024

This PR Is chained (includes all commit from) #16995.

The companion roottest PR is root-project/roottest#1226

It also requires an increase in the TStreamerInfo class version number (to mark which files/StreamerInfo have weird data for non-default size enum and which files are correct).

This fixes #16312. However files produced without this PR and with enum with a non default size will have data that is incorrectly saved but potential recoverable. The way the data is written will dependent on the size of the enum at the time of writing. Since this size is not recorded in the file, we can not have a general solution to read those corrupted files. However when that enum size used at write time is known, the techniques described here and here can be used to recover those weird files.

If reading both the corrupted files (using the above mentioned work-around) and the new files (correctly written with this PR) the recommendation is to increase the version number of the classes that contain an enum with non-default size so that the rules or custom streamer can distinguish the old and new files.

This enables the StreamerInfoActions to enable the shortcuts that
are possible in that case.
The version recorded 'here' is the version of the TStreamerInfo class not the user class
Even without schema evolution, the representation of a collection of enums
on file is a `vector<int>` so `TStreamerElement::fType` and `TStreamerElement::fClassObject`
should point to `vector<int>` while `TStreamerElement::fNewType` and
`TStreamerElement::fNewClass` should point to the current in memory representaition
`actualCollectionType< actualEnum >` that will know/remember what is the actual enum
in memory representation.
Combine the code with the one use for the text actions
Combine the code with the one use for the text actions
To use be for case where the read and write implementation differs only slightly
To be used for function template that can be used for more than one actual looper (usually in
conjunction with the LoopOverCollection template
Allow to share code with the collection loopers.
This required the addition of a concept that can be used to reduce boiler plate duplication.
We now have an example where a generic function (Read/WriteStreamerLoop) is used with action
with different signature by leveraging template arguments packs and a using statement declaration
within the *Looper helper structs
@pcanal pcanal self-assigned this Nov 22, 2024
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github-actions bot commented Nov 22, 2024

Test Results

    18 files      18 suites   4d 15h 40m 1s ⏱️
 2 684 tests  2 684 ✅ 0 💤 0 ❌
46 474 runs  46 474 ✅ 0 💤 0 ❌

Results for commit 54ae470.

♻️ This comment has been updated with latest results.

Using the new bit kBitsIsValid.
This allows to both store the validity in the rootpcm file and also to execute IsValid
on a TEnum read from a rootpcm without doing a Clang lookup
I.e. take into account the non-default size of an enum declaration
We split the reprensentation of a collection of enums between in memory
representation and onfile representation (always `vector<int>`).
Similarly for data member that enum types we set the in memory type (`NewType`)
to be correct and keep the onfile type (`fType`) as it was (`Int_t`)
@pcanal pcanal changed the title WIP: Add support for enums with non-default size Add support for enums with non-default size Nov 22, 2024
@pcanal pcanal marked this pull request as ready for review November 22, 2024 22:50
@pcanal pcanal requested a review from dpiparo as a code owner November 22, 2024 22:50
@pcanal pcanal requested a review from jblomer November 22, 2024 22:50
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pcanal commented Nov 22, 2024

@ktf This ready for further testing and will be merged once the reviews are done.

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Broken streaming of vector of enum with underlying type other than int
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