ORC-1315:[C++] Fix byte to integer conversions fail on platforms with unsigned char type

[luffy-zh]

What changes were proposed in this pull request?

This patch adds static_cast for the char type cast in RLE/ColumnReader.

Why are the changes needed?

For the context of ORC-1315, this patch fixes signed char to unsigned char conversions fail where char is by default unsigned.

How was this patch tested?

No new tests were added.

[dongjoon-hyun]

Thank you for making a PR, @luffy-zh . BTW, according to the JIRA, do we need this at Apache ORC 1.8.1?

cc @wgtmac , @stiga-huang , @williamhyun .

[wgtmac]

I believe we need to port to 1.8.1. @dongjoon-hyun

[dongjoon-hyun]

Got it. Thanks, @wgtmac .

[coderex2522]

+1, LGTM.

[dongjoon-hyun]

Hi, @wgtmac . Is there a reason why this is not backported to branch-1.8?

I believe we need to port to 1.8.1. @dongjoon-hyun

And, do we need 2 patches to be complete for ORC-1315?

$ git log --oneline main | grep ORC-1315
91ded769 ORC-1315: [C++] Fix test failure when unsigned char is in effect
acb8d6ca ORC-1315: [C++] Fix byte to integer conversion failure on platforms with unsigned char type

[dongjoon-hyun]

Sorry, I was confused. I found your comment, #1318 (comment)

I can confirm that this issue only exists in the main branch, therefore we don't need backport the fix to branch-1.8.

I'll change the milestone of this PR.