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From Benjamin Bannier <benjamin.bann...@mesosphere.io>
Subject Re: Review Request 46821: Avoided slicing of flags in subprocess in libprocess and stout.
Date Sun, 03 Jul 2016 15:22:28 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/46821/
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(Updated July 3, 2016, 5:22 p.m.)


Review request for mesos, Alexander Rukletsov, Joris Van Remoortere, Michael Park, and Vinod
Kone.


Changes
-------

Rebased.


Summary (updated)
-----------------

Avoided slicing of flags in subprocess in libprocess and stout.


Bugs: MESOS-3335
    https://issues.apache.org/jira/browse/MESOS-3335


Repository: mesos


Description
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While `FlagsBase` internally stores just maps of names and
flags, the functions stored in a `Flag` rely on the original type of
the `Flags` containing them (e.g., we perform dynamic casts to detect
their types).

Since `Option<T>` stores `T` as a value (i.e., it cannot contain
reference types) any interface taking an `Option<T>` cannot rely on
polymorphic behavior of `T`. To make use of polymorphism we should
instead store e.g., a pointer type to avoid slicing.

Here we change `Flags` arguments of `subprocess` to allow preserving
the original type so `Flag` function can work reliably. We do this by
passing a `Shared<Flags>` so we do not restrict copying; not that it
would also be possible to use an `Owned<Flags>`, but this would
require an audit of all sites where the arguments are used as
`Owned<T>` should not be copied, but do not prevent that on their own.


Diffs (updated)
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  3rdparty/libprocess/include/process/subprocess_base.hpp e0c6b2d930fbd2cfe011e6faf44843b83ab1db27

  3rdparty/libprocess/src/subprocess.cpp 44073146118b6c6e9e730b8c901852594080a3eb 
  3rdparty/libprocess/src/subprocess_windows.cpp d4713ec9d6cdc3caca6e62d882c9efcb754c2017

  3rdparty/libprocess/src/tests/subprocess_tests.cpp 3f3e21514bd5e2e388165eb64d540764097557ac


Diff: https://reviews.apache.org/r/46821/diff/


Testing
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Tested on various platforms in internal CI.


Thanks,

Benjamin Bannier


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