[flang] [flang-rt] Subscript overrun in namelists during a READ command.

[kwyatt-ext]

If a bad subscript is provided in a namelisted record, the HandleSubscripts() routine can read off into infinity. This patch ensures that a read will not go beyond the rank of the expected variable.

The failure will then be captured in the return status (IOSTAT) of the READ.

The small test demonstrates the failure before and after the fix.

[github-actions]

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[kwyatt-ext]

Hello @sscalpone . I believe I am supposed to ping you for this fix. This is my first one. Thanks.

[kwyatt-ext]

Closing this PR as labels were not properly created. I will reopen to allow the automated labelling to occur.