RFR: 8290373: Enable lossy conversion warnings on Windows [v3]

[Andrew Haley]

On Wed, 20 Jul 2022 14:42:44 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> This change was mostly applied mechanically by parsing the build log, and then using a script to insert these lines, with a manual review + 1 or 2 fixups. Making sure the inserted `checked_cast`s are correct seems much harder.

It is.

> I think having `PRAGMA_ALLOW_LOSSY_CONVERSIONS` in the file also sends a much clearer message that: warnings in this file have not been looked at/fixed yet, which I don't think `checked_cast` does.

It kinda would, because such casts would have to be considered. But OK.

> The approach I've taken preserves the current behavior of the code, but it also allows for fixing these warnings on a per-file basis (besides enabling the warning for the 800 or so files that don't have warnings right now). This seems to me like an easier and safer way to make progress.

OK, so this is hopefully a temporary fix.

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PR: https://git.openjdk.org/jdk/pull/9516