[llvm] [flang] [flang-rt] Subscript overrun could occur in namelists during a READ command. (PR #176959)

[via llvm-commits]

kwyatt-ext wrote:

Here are the test artifacts for this change:

**check-flang**:
`Testing Time: 141.34s

Total Discovered Tests: 4239
  Unsupported      :   81 (1.91%)
  Passed           : 4147 (97.83%)
  Expectedly Failed:   11 (0.26%)


FLANG Container Test completed 3 minutes (201 s).

Total Time: 3 minutes (201 s)
Completed : Tue Mar  3 11:20:53 AM CST 2026`

**check-flang-rt**:
`Testing Time: 1.59s

Total Discovered Tests: 279
  Passed: 279 (100.00%)


FLANG Container Test completed 0 minutes (58 s).

Total Time: 0 minutes (58 s)
Completed : Tue Mar  3 11:23:24 AM CST 2026`

**llvm-test-suite**:
`Testing Time: 218.56s

Total Discovered Tests: 6931
  Passed: 6931 (100.00%)


LLVM Test Suite Container Test completed in 3 minutes (223 s).

Total Time: 3 minutes (223 s)
Completed : Tue Mar  3 11:00:50 AM CST 2026`


https://github.com/llvm/llvm-project/pull/176959