Re: portability patch for io/ftw.c

[Jim Meyering]

Ulrich Drepper <address@hidden> wrote:
> Jim Meyering wrote:
>
>> +#if defined _LIBC
...
>> +#else
>> +# if HAVE_DIRENT_H || defined _LIBC
...
> This part is not correct.

True, but it is also harmless.
I'll remove the `|| defined _LIBC'.
Thanks.

> First, why a || defined _libc in the #else branch?

That's probably a vestige of my first attempt to adapt the
usually-considered-sufficiently-general code to the special
case of glib/_LIBC.  IMHO, we shouldn't have to make such
exceptions and litter otherwise-clean code with cpp conditionals
involving _LIBC.  end of rant :-)

> Second, I doubt you can rely on d_namlen for all platforms without
> <dirent.h>.  And vice versa: there are platforms which have <dirent.h>
> and which define an appropriate field, making the strlen() call unnecessary.

If you can point to such a system, please let everyone know.
That code has been used in the GNU tools I maintain for a long
time, without causing any problems, afaik.  Similarly, it made
it into the autoconf manual, so I suspect if there were a significant
problem with it, it would have been addressed by now.

As for being optimal, there may be a few proprietary systems on which
the strlen is not strictly necessary, but I don't want to spend my
time finding them and optimizing this code to accommodate them.

...
> You remove the __getcwd from the first #ifndef _LIBC block just to add
> it in a directly following new #ifndef _LIBC block?  Please keep the
> changes to a minimum.

I'm sure you noticed that the lines I removed were not the
same as the ones I added.
I thought the case of getcwd was sufficiently different that it
deserved to be separate, but it'd be better to do the same thing
with a couple blank lines.

Here's a new patch:

2003-02-07  Jim Meyering  <address@hidden>

        * io/ftw.c: Add autoconf-recommended block of alloca-related code.
        Include autoconf-recommended block of dirent/NAMELEN-related
        definitions and includes.  Use NAMELEN throughout, rather than
        _D_EXACT_NAMLEN.
        [_LIBC]: Define NAMELEN to _D_EXACT_NAMLEN.
        [!_LIBC] (__getcwd): Define to xgetcwd and declare xgetcwd.
        (stpcpy): Declare, if necessary.
        (mempcpy): Define, if necessary.
        [!_LIBC] (__stpcpy, __mempcpy): Define.
        [!_LIBC] (LXSTAT, XSTAT): Define.
        (lstat) [!LIBC && !LSTAT_FOLLOWS_SLASHED_SYMLINK]: Define to rpl_lstat.
        (find_object): Don't use c99-style struct initializer.
        Tweak wording in a couple comments.

Index: io/ftw.c
===================================================================
RCS file: /cvs/glibc/libc/io/ftw.c,v
retrieving revision 1.40
diff -u -p -u -p -r1.40 ftw.c
--- io/ftw.c    5 Feb 2003 17:46:12 -0000       1.40
+++ io/ftw.c    7 Feb 2003 21:04:10 -0000
@@ -22,7 +22,42 @@
 # include <config.h>
 #endif
 
-#include <dirent.h>
+#if __GNUC__
+# define alloca __builtin_alloca
+#else
+# if HAVE_ALLOCA_H
+#  include <alloca.h>
+# else
+#  ifdef _AIX
+ #  pragma alloca
+#  else
+char *alloca ();
+#  endif
+# endif
+#endif
+
+#if defined _LIBC
+# include <dirent.h>
+# define NAMLEN(dirent) _D_EXACT_NAMLEN(dirent)
+#else
+# if HAVE_DIRENT_H
+#  include <dirent.h>
+#  define NAMLEN(dirent) strlen ((dirent)->d_name)
+# else
+#  define dirent direct
+#  define NAMLEN(dirent) (dirent)->d_namlen
+#  if HAVE_SYS_NDIR_H
+#   include <sys/ndir.h>
+#  endif
+#  if HAVE_SYS_DIR_H
+#   include <sys/dir.h>
+#  endif
+#  if HAVE_NDIR_H
+#   include <ndir.h>
+#  endif
+# endif
+#endif
+
 #include <errno.h>
 #include <ftw.h>
 #include <limits.h>
@@ -39,6 +74,15 @@
 # include <sys/stat.h>
 #endif
 
+#if ! _LIBC && !HAVE_DECL_STPCPY && !defined stpcpy
+char *stpcpy ();
+#endif
+
+#if ! _LIBC && ! defined HAVE_MEMPCPY && ! defined mempcpy
+/* Be CAREFUL that there are no side effects in N.  */
+# define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
+#endif
+
 /* #define NDEBUG 1 */
 #include <assert.h>
 
@@ -49,8 +93,11 @@
 # define __closedir closedir
 # undef __fchdir
 # define __fchdir fchdir
+
 # undef __getcwd
-# define __getcwd getcwd
+# define __getcwd(P, N) xgetcwd ()
+extern char *xgetcwd (void);
+
 # undef __opendir
 # define __opendir opendir
 # undef __readdir64
@@ -61,6 +108,10 @@
 # define __tfind tfind
 # undef __tsearch
 # define __tsearch tsearch
+# undef __stpcpy
+# define __stpcpy stpcpy
+# undef __mempcpy
+# define __mempcpy mempcpy
 # undef internal_function
 # define internal_function /* empty */
 # undef dirent64
@@ -69,6 +120,15 @@
 # define MAX(a, b) ((a) > (b) ? (a) : (b))
 #endif
 
+/* Arrange to make lstat calls go through the wrapper function
+   on systems with an lstat function that does not dereference symlinks
+   that are specified with a trailing slash.  */
+#if ! _LIBC && ! LSTAT_FOLLOWS_SLASHED_SYMLINK
+int rpl_lstat (const char *, struct stat *);
+# undef lstat
+# define lstat(Name, Stat_buf) rpl_lstat(Name, Stat_buf)
+#endif
+
 #ifndef __set_errno
 # define __set_errno(Val) errno = (Val)
 #endif
@@ -79,8 +139,13 @@
 # define NFTW_NAME nftw
 # define INO_T ino_t
 # define STAT stat
-# define LXSTAT __lxstat
-# define XSTAT __xstat
+# ifdef _LIBC
+#  define LXSTAT __lxstat
+#  define XSTAT __xstat
+# else
+#  define LXSTAT(V,f,sb) lstat (f,sb)
+#  define XSTAT(V,f,sb) stat (f,sb)
+# endif
 # define FTW_FUNC_T __ftw_func_t
 # define NFTW_FUNC_T __nftw_func_t
 #endif
@@ -124,7 +189,7 @@ struct ftw_data
   int flags;
 
   /* Conversion array for flag values.  It is the identity mapping for
-     `nftw' calls, otherwise it maps the values to those know by
+     `nftw' calls, otherwise it maps the values to those known by
      `ftw'.  */
   const int *cvt_arr;
 
@@ -140,9 +205,8 @@ struct ftw_data
 };
 
 
-/* Internally we use the FTW_* constants used for `nftw'.  When the
-   process called `ftw' we must reduce the flag to the known flags
-   for `ftw'.  */
+/* Internally we use the FTW_* constants used for `nftw'.  When invoked
+   as `ftw', map each flag to the subset of values used by `ftw'.  */
 static const int nftw_arr[] =
 {
   FTW_F, FTW_D, FTW_DNR, FTW_NS, FTW_SL, FTW_DP, FTW_SLN
@@ -188,7 +252,9 @@ add_object (struct ftw_data *data, struc
 static inline int
 find_object (struct ftw_data *data, struct STAT *st)
 {
-  struct known_object obj = { .dev = st->st_dev, .ino = st->st_ino };
+  struct known_object obj;
+  obj.dev = st->st_dev;
+  obj.ino = st->st_ino;
   return __tfind (&obj, &data->known_objects, object_compare) != NULL;
 }
 
@@ -216,7 +282,7 @@ open_dir_stream (struct ftw_data *data, 
 
          while ((d = __readdir64 (st)) != NULL)
            {
-             size_t this_len = _D_EXACT_NAMLEN (d);
+             size_t this_len = NAMLEN (d);
              if (actsize + this_len + 2 >= bufsize)
                {
                  char *newp;
@@ -354,7 +420,7 @@ process_entry (struct ftw_data *data, st
 
              if (result == 0 && (data->flags & FTW_CHDIR))
                {
-                 /* Change back to current directory.  */
+                 /* Change back to parent directory.  */
                  int done = 0;
                  if (dir->stream != NULL)
                    if (__fchdir (dirfd (dir->stream)) == 0)
@@ -452,7 +518,7 @@ ftw_dir (struct ftw_data *data, struct S
 
   while (dir.stream != NULL && (d = __readdir64 (dir.stream)) != NULL)
     {
-      result = process_entry (data, &dir, d->d_name, _D_EXACT_NAMLEN (d));
+      result = process_entry (data, &dir, d->d_name, NAMLEN (d));
       if (result != 0)
        break;
     }

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