csplit: avoid negate-with-overflow on an i32::MIN regex line offset

src/uu/csplit/src/csplit.rs

@@ -480,7 +480,7 @@ impl SplitWriter<'_> {
             // but do not rewind it either since no match should be done within.
             // The consequence is that the buffer may already be full with lines from a previous
             // split, which is taken care of when calling `shrink_buffer_to_size`.
-            let offset_usize = -offset as usize;
+            let offset_usize = offset.unsigned_abs() as usize;
             input_iter.set_size_of_buffer(offset_usize);
             while let Some((ln, line)) = input_iter.next() {
                 let line = line?;

tests/by-util/test_csplit.rs

@@ -236,6 +236,22 @@ fn test_up_to_match_negative_offset() {
     assert_eq!(at.read("xx01"), generate(6, 51));
 }
 
+#[test]
+fn test_up_to_match_negative_offset_min_i32() {
+    new_ucmd!()
+        .args(&["numbers50.txt", "/45/-2147483648"])
+        .fails()
+        .stderr_is("csplit: '/45/-2147483648': line number out of range\n");
+}
+
+#[test]
+fn test_skip_to_match_negative_offset_min_i32() {
+    new_ucmd!()
+        .args(&["numbers50.txt", "%45%-2147483648"])
+        .fails()
+        .stderr_is("csplit: '%45%-2147483648': line number out of range\n");
+}
+
 #[test]
 fn test_up_to_match_negative_offset_repeat_twice() {
     let (at, mut ucmd) = at_and_ucmd!();