maint: avoid "definitely lost" valgrind warnings

Since commit v8.23-19-g8defcee, main() will return,
rather than call exit(), this inducing "definitely lost"
warnings in valgrind's leak checker.  That precludes using
the following to flag memory leaks:

  valgrind --leak-check=full --error-exitcode=1 \
           --errors-for-leak-kinds=definite

* src/pr.c (main): In dev builds, explicitly free memory allocated.
* src/sort.c (main): Likewise.
* src/tail.c (main): Likewise.
* src/tsort.c (tsort): Likewise.

4 files changed, 7 insertions, 0 deletions

diff --git a/src/pr.c b/src/pr.c
index d79d84f18..887e12584 100644
--- a/src/pr.c
+++ b/src/pr.c
@@ -1130,6 +1130,7 @@ main (int argc, char **argv)
     }
 
   cleanup ();
+  IF_LINT (free (file_names));
 
   if (have_read_stdin && fclose (stdin) == EOF)
     error (EXIT_FAILURE, errno, _("standard input"));
diff --git a/src/sort.c b/src/sort.c
index 85fc38f73..a7eda8325 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -4742,6 +4742,8 @@ main (int argc, char **argv)
       sort (files, nfiles, outfile, nthreads);
     }
 
+  IF_LINT (free (files));
+
   if (have_read_stdin && fclose (stdin) == EOF)
     die (_("close failed"), "-");
 
diff --git a/src/tail.c b/src/tail.c
index c062d403f..f916d7460 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -2354,6 +2354,8 @@ main (int argc, char **argv)
       tail_forever (F, n_files, sleep_interval);
     }
 
+  IF_LINT (free (F));
+
   if (have_read_stdin && close (STDIN_FILENO) < 0)
     error (EXIT_FAILURE, errno, "-");
   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
diff --git a/src/tsort.c b/src/tsort.c
index d4be03d42..0533451da 100644
--- a/src/tsort.c
+++ b/src/tsort.c
@@ -528,6 +528,8 @@ tsort (const char *file)
         }
     }
 
+  IF_LINT (free (root));
+
   if (fclose (stdin) != 0)
     error (EXIT_FAILURE, errno, "%s",
            is_stdin ? _("standard input") : quote (file));