pr: guard input position update against overflow

* src/pr.c (char_to_clump): Use ckd_add() and report integer overflow.
* tests/pr/options.sh: Add a test case.
* NEWS: Mention the bug fix.
Fixes https://bugs.gnu.org/81393

NEWS

@@ -26,6 +26,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   standard output is fully buffered, e.g., when redirected to a file.
   [bug introduced in coreutils-9.10]
 
+  'pr' now exits gracefully upon exceeding internal accounting limits,
+  like when processing large tab stops.
+  [This bug was present in "the beginning".]
+
   'shred' no longer blocks when opening a FIFO that has no readers.
   [This bug was present in "the beginning".]
 

src/pr.c

@@ -2732,7 +2732,10 @@ char_to_clump (char c)
   else if (width < 0 && input_position <= -width)
     input_position = 0;
   else
-    input_position += width;
+    {
+      if (ckd_add (&input_position, input_position, width))
+        integer_overflow ();
+    }
 
   return chars;
 }

tests/pr/options.sh

@@ -57,4 +57,15 @@ printf '%s\n' "pr: '-e' extra characters or $INV in the argument: '-1'" \
  >exp || framework_failure_
 compare exp err || fail=1
 
+# Ensure we exit gracefully upon internal overflow limits
+# Tag as expensive as it uses little mem, but about 10s on a 2020 class machine.
+if { test "$RUN_VERY_EXPENSIVE_TESTS" = yes ||
+     test "$RUN_EXPENSIVE_TESTS" = yes; } &&
+   test "$INT_MAX" = 2147483647; then  # restrict to usual 32 bit limits
+  head -c1M /dev/zero | tr '\0' '\t' |
+  returns_ 1 pr -t -e$(($INT_MAX/(1024*1024) + 1)) 2>err >/dev/null || fail=1
+  printf '%s\n' "pr: integer overflow" > exp || framework_failure_
+  compare exp err || fail=1
+fi
+
 Exit $fail