add test for #4334 (space leak in Data.List.lines)

testsuite/tests/ghc-regress/perf/space_leaks/T4334.hs

+module Main (main) where
+
+import System.Environment (getArgs)
+
+mkText :: Int -> Int -> Char -> String
+mkText ll ln c =
+    unlines $ [replicate k c | k <- [ll .. ll+ln]]
+
+main :: IO ()
+main = do
+    args <- getArgs
+    let (ll, ln, c) =
+          case args of
+            (a1:a2:a3:_) -> (read a1, read a2, head a3)
+            (a1:a2:_)    -> (read a1, read a2, 'a')
+            (a1:_)       -> (read a1, 3, 'b')
+            _            -> (100000, 5, 'c')
+    mapM_ (print . length) (lines $ mkText ll ln c)

testsuite/tests/ghc-regress/perf/space_leaks/T4334.stdout

+1000000
+1000001
+1000002

testsuite/tests/ghc-regress/perf/space_leaks/all.T

@@ -21,3 +21,11 @@ test('space_leak_001',
      compile_and_run,
      [''])
 
+test('T4334',
+     # Test for a space leak in Data.List.lines (fixed with #4334)
+     [extra_run_opts('1000000 2 t'),
+      stats_num_field('peak_megabytes_allocated', 1, 3),
+      # prof ways don't work well with +RTS -V0
+      omit_ways(['profc','profasm','profthreaded'])
+      ],
+     compile_and_run, [''])