[jira] [Commented] (ARROW-8328) [C++] MSVC is not respecting warning-disable flags

["Antoine Pitrou (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-8328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17074740#comment-17074740 ] 

Antoine Pitrou commented on ARROW-8328:
---------------------------------------

Hmm, I don't think we disable all conversion warnings. MSVC is actually useful to find instances of implicit downcasting.

> [C++] MSVC is not respecting warning-disable flags
> --------------------------------------------------
>
>                 Key: ARROW-8328
>                 URL: https://issues.apache.org/jira/browse/ARROW-8328
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>    Affects Versions: 0.16.0
>            Reporter: Ben Kietzman
>            Assignee: Ben Kietzman
>            Priority: Major
>             Fix For: 1.0.0
>
>
> We provide [warning-disabling flags to MSVC|https://github.com/apache/arrow/blob/72433c6/cpp/cmake_modules/SetupCxxFlags.cmake#L151-L153] including one which should disable all conversion warnings. However this is not completely effectual and Appveyor will still emit conversion warnings (which are then treated as errors), requiring insertion of otherwise unnecessary explicit casts or {{#pragma}}s (for example https://github.com/apache/arrow/pull/6820 ).
> Perhaps flag ordering is significant? In any case, as we have conversion warnings disabled for other compilers we should ensure they are completely disabled for MSVC as well.



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