Add Unix.realpath.

Binds to realpath(3) on POSIX and GetFinalPathNameByHandle on
Windows.

Changes

@@ -15,6 +15,9 @@ Working version
 
 ### Other libraries:
 
+- #XXXX Add `Unix.realpath`
+  (Daniel Bünzli, review by XXX)
+
 ### Tools:
 
 ### Manual and documentation:

configure.ac

@@ -1343,6 +1343,8 @@ AC_CHECK_FUNC([symlink],
   [AC_CHECK_FUNC([readlink],
     [AC_CHECK_FUNC([lstat], [AC_DEFINE([HAS_SYMLINK])])])])
 
+AC_CHECK_FUNC([realpath], [AC_DEFINE([HAS_REALPATH])])
+
 # wait
 AC_CHECK_FUNC(
   [waitpid],

otherlibs/unix/Makefile

@@ -35,7 +35,7 @@ COBJS=accept.o access.o addrofstr.o alarm.o bind.o channels.o chdir.o \
   gettimeofday.o getserv.o getsockname.o getuid.o gmtime.o \
   initgroups.o isatty.o itimer.o kill.o link.o listen.o lockf.o lseek.o \
   mkdir.o mkfifo.o mmap.o mmap_ba.o \
-  nice.o open.o opendir.o pipe.o putenv.o read.o \
+  nice.o open.o opendir.o pipe.o putenv.o read.o realpath.o \
   readdir.o readlink.o rename.o rewinddir.o rmdir.o select.o sendrecv.o \
   setgid.o setgroups.o setsid.o setuid.o shutdown.o signals.o \
   sleep.o socket.o socketaddr.o \

otherlibs/unix/realpath.c

@@ -0,0 +1,43 @@
+/**************************************************************************/
+/*                                                                        */
+/*                                 OCaml                                  */
+/*                                                                        */
+/*                         The OCaml programmers                          */
+/*                                                                        */
+/*   Copyright 2020 Institut National de Recherche en Informatique et     */
+/*     en Automatique.                                                    */
+/*                                                                        */
+/*   All rights reserved.  This file is distributed under the terms of    */
+/*   the GNU Lesser General Public License version 2.1, with the          */
+/*   special exception on linking described in the file LICENSE.          */
+/*                                                                        */
+/**************************************************************************/
+
+#include <caml/mlvalues.h>
+#include <caml/memory.h>
+#include <caml/alloc.h>
+#include <caml/fail.h>
+#include "unixsupport.h"
+
+#ifdef HAS_REALPATH
+
+CAMLprim value unix_realpath (value p)
+{
+  CAMLparam1 (p);
+  char *r;
+  value rp;
+
+  caml_unix_check_path (p, "realpath");
+  r = realpath (String_val (p), NULL);
+  if (r == NULL) { uerror ("realpath", p); }
+  rp = caml_copy_string (r);
+  free (r);
+  CAMLreturn (rp);
+}
+
+#else
+
+CAMLprim value unix_realpath (value p)
+{ caml_invalid_argument ("realpath not implemented"); }
+
+#endif

otherlibs/unix/unix.ml

@@ -322,6 +322,7 @@ external isatty : file_descr -> bool = "unix_isatty"
 external unlink : string -> unit = "unix_unlink"
 external rename : string -> string -> unit = "unix_rename"
 external link : ?follow:bool -> string -> string -> unit = "unix_link"
+external realpath : string -> string = "unix_realpath"
 
 module LargeFile =
   struct

otherlibs/unix/unix.mli

@@ -622,6 +622,11 @@ val link : ?follow (* thwart tools/sync_stdlib_docs *) :bool ->
                  unavailable.
    @raise ENOSYS On {e Windows} if [~follow:false] is requested. *)
 
+val realpath : string -> string
+(** [realpath p] is the absolute pathname for [p] obtained by resolving
+    all extra [/] characters, relative path segments and symbolic links.
+
+    @since 4.13.0 *)
 
 (** {1 File permissions and ownership} *)
 

otherlibs/unix/unixLabels.mli

@@ -622,6 +622,11 @@ val link : ?follow (* thwart tools/sync_stdlib_docs *) :bool ->
                  unavailable.
    @raise ENOSYS On {e Windows} if [~follow:false] is requested. *)
 
+val realpath : string -> string
+(** [realpath p] is the absolute pathname for [p] obtained by resolving
+    all extra [/] characters, relative path segments and symbolic links.
+
+    @since 4.13.0 *)
 
 (** {1 File permissions and ownership} *)
 

otherlibs/win32unix/Makefile

@@ -23,7 +23,7 @@ WIN_FILES = accept.c bind.c channels.c close.c \
   getpeername.c getpid.c getsockname.c gettimeofday.c isatty.c \
   link.c listen.c lockf.c lseek.c nonblock.c \
   mmap.c open.c pipe.c read.c readlink.c rename.c \
-  select.c sendrecv.c \
+  realpath.c select.c sendrecv.c \
   shutdown.c sleep.c socket.c sockopt.c startup.c stat.c \
   symlink.c system.c times.c truncate.c unixsupport.c windir.c winwait.c \
   write.c winlist.c winworker.c windbug.c utimes.c

otherlibs/win32unix/realpath.c

@@ -0,0 +1,73 @@
+/**************************************************************************/
+/*                                                                        */
+/*                                 OCaml                                  */
+/*                                                                        */
+/*                         The OCaml programmers                          */
+/*                                                                        */
+/*   Copyright 2020 Institut National de Recherche en Informatique et     */
+/*     en Automatique.                                                    */
+/*                                                                        */
+/*   All rights reserved.  This file is distributed under the terms of    */
+/*   the GNU Lesser General Public License version 2.1, with the          */
+/*   special exception on linking described in the file LICENSE.          */
+/*                                                                        */
+/**************************************************************************/
+
+#define CAML_INTERNALS
+
+#include <caml/mlvalues.h>
+#include <caml/memory.h>
+#include <caml/alloc.h>
+#include <caml/fail.h>
+#include <caml/osdeps.h>
+#include "unixsupport.h"
+
+#include <windows.h>
+#include <fileapi.h>
+#include <stdio.h>
+
+CAMLprim value unix_realpath (value p)
+{
+  CAMLparam1 (p);
+  HANDLE h;
+  wchar_t *wp;
+  wchar_t *wr;
+  DWORD wr_len;
+  value rp;
+
+  caml_unix_check_path (p, "realpath");
+  wp = caml_stat_strdup_to_utf16 (String_val (p));
+  h = CreateFile (wp, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
+                  FILE_ATTRIBUTE_NORMAL, NULL);
+  caml_stat_free (wp);
+
+  if (h == INVALID_HANDLE_VALUE)
+  {
+    win32_maperr (GetLastError ());
+    uerror ("realpath", p);
+  }
+
+  wr_len = GetFinalPathNameByHandle (h, NULL, 0, VOLUME_NAME_DOS);
+  if (wr_len == 0)
+  {
+    win32_maperr (GetLastError ());
+    CloseHandle (h);
+    uerror ("realpath", p);
+  }
+
+  wr = caml_stat_alloc ((wr_len + 1) * sizeof (wchar_t));
+  wr_len = GetFinalPathNameByHandle (h, wr, wr_len, VOLUME_NAME_DOS);
+
+  if (wr_len == 0)
+  {
+    win32_maperr (GetLastError ());
+    CloseHandle (h);
+    caml_stat_free (wr);
+    uerror ("realpath", p);
+  }
+
+  rp = caml_copy_string_of_utf16 (wr);
+  CloseHandle (h);
+  caml_stat_free (wr);
+  CAMLreturn (rp);
+}

otherlibs/win32unix/unix.ml

@@ -364,6 +364,7 @@ external isatty : file_descr -> bool = "unix_isatty"
 external unlink : string -> unit = "unix_unlink"
 external rename : string -> string -> unit = "unix_rename"
 external link : ?follow:bool -> string -> string -> unit = "unix_link"
+external realpath : string -> string = "unix_realpath"
 
 (* Operations on large files *)
 

runtime/caml/s.h.in

@@ -141,6 +141,9 @@
 
 /* Define HAS_SYMLINK if you have symlink() and readlink() and lstat(). */
 
+#undef HAS_REALPATH
+/* Define HAS_REALPATH if you have realpath(). */
+
 #undef HAS_WAIT4
 #undef HAS_WAITPID