FYI: fts.c minor readability improvement

[Jim Meyering]

I've just checked in this change:

        Slight readability improvement: use an assert-like macro
        in place of literal "abort ()" uses.
        * lib/fts.c (fts_assert): Define.
        (fts_set_stat_required, cwd_advance_fd, fts_read, fd_ring_check):
        Use this macro instead of a bare 'abort'.

Index: lib/fts.c
===================================================================
RCS file: /sources/gnulib/gnulib/lib/fts.c,v
retrieving revision 1.30
diff -u -p -r1.30 fts.c
--- lib/fts.c   3 Dec 2006 10:23:10 -0000       1.30
+++ lib/fts.c   8 Jan 2007 10:29:56 -0000
@@ -1,6 +1,6 @@
 /* Traverse a file hierarchy.

-   Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -138,6 +138,18 @@ enum Fts_stat
 # define HAVE_OPENAT_SUPPORT 0
 #endif

+#ifdef NDEBUG
+# define fts_assert(expr) ((void) 0)
+#else
+# define fts_assert(expr)      \
+    do                         \
+      {                                \
+       if (!(expr))            \
+         abort ();             \
+      }                                \
+    while (false)
+#endif
+
 static FTSENT  *fts_alloc (FTS *, const char *, size_t) internal_function;
 static FTSENT  *fts_build (FTS *, int) internal_function;
 static void     fts_lfree (FTSENT *) internal_function;
@@ -236,8 +248,7 @@ fd_ring_clear (I_ring *fd_ring)
 static void
 fts_set_stat_required (FTSENT *p, bool required)
 {
-  if (p->fts_info != FTS_NSOK)
-    abort ();
+  fts_assert (p->fts_info == FTS_NSOK);
   p->fts_statp->st_size = (required
                           ? FTS_STAT_REQUIRED
                           : FTS_NO_STAT_REQUIRED);
@@ -274,8 +285,7 @@ internal_function
 cwd_advance_fd (FTS *sp, int fd, bool chdir_down_one)
 {
   int old = sp->fts_cwd_fd;
-  if (old == fd && old != AT_FDCWD)
-    abort ();
+  fts_assert (old != fd || old == AT_FDCWD);

   if (chdir_down_one)
     {
@@ -739,7 +749,7 @@ check_for_dir:
                      case FTS_NO_STAT_REQUIRED:
                        break;
                      default:
-                       abort ();
+                       fts_assert (0);
                      }
                  }

@@ -775,8 +785,7 @@ check_for_dir:
                return (sp->fts_cur = NULL);
        }

-       if (p->fts_info == FTS_NSOK)
-         abort ();
+       fts_assert (p->fts_info != FTS_NSOK);

        /* NUL terminate the file name.  */
        sp->fts_path[p->fts_pathlen] = '\0';
@@ -1345,7 +1354,7 @@ fd_ring_check (FTS const *sp)
              error (0, errno, "parent: %s", c2);
              free (cwd);
              free (c2);
-             abort ();
+             fts_assert (0);
            }
          close (cwd_fd);
          cwd_fd = parent_fd;