Provide euidaccess, canonicalize_file_name; fix fchmodat.

* syscalls.cc (fchmodat): lchmod is not yet implemented.
(euidaccess): New function.
* path.cc (realpath): Update comment.
(canonicalize_file_name): New function.
* include/cygwin/stdlib.h (canonicalize_file_name): Declare it.
* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump.
* cygwin.din: Export canonicalize_file_name, eaccess, euidaccess.
* posix.sgml: Mention them.

winsup/cygwin/ChangeLog

@@ -1,3 +1,14 @@
+2009-09-25  Eric Blake  <ebb9@byu.net>
+
+	* syscalls.cc (fchmodat): lchmod is not yet implemented.
+	(euidaccess): New function.
+	* path.cc (realpath): Update comment.
+	(canonicalize_file_name): New function.
+	* include/cygwin/stdlib.h (canonicalize_file_name): Declare it.
+	* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump.
+	* cygwin.din: Export canonicalize_file_name, eaccess, euidaccess.
+	* posix.sgml: Mention them.
+
 2009-09-25  Eric Blake  <ebb9@byu.net>
 
 	* fhandler.h (fhandler_base::fhaccess): Add parameter.

winsup/cygwin/cygwin.din

@@ -165,6 +165,7 @@ cabsf NOSIGFE
 _cabsf = cabsf NOSIGFE
 calloc SIGFE
 _calloc = calloc SIGFE
+canonicalize_file_name SIGFE
 cbrt NOSIGFE
 _cbrt = cbrt NOSIGFE
 cbrtf NOSIGFE
@@ -296,6 +297,7 @@ dup SIGFE
 _dup = dup SIGFE
 dup2 SIGFE
 _dup2 = dup2 SIGFE
+eaccess = euidaccess SIGFE
 ecvt SIGFE
 _ecvt = ecvt SIGFE
 ecvtbuf SIGFE
@@ -341,6 +343,7 @@ _erff = erff NOSIGFE
 err SIGFE
 __errno NOSIGFE
 errx SIGFE
+euidaccess SIGFE
 execl SIGFE
 _execl = execl SIGFE
 execle SIGFE

winsup/cygwin/include/cygwin/stdlib.h

@@ -1,6 +1,6 @@
 /* stdlib.h
 
-   Copyright 2005, 2006, 2007 Red Hat Inc.
+   Copyright 2005, 2006, 2007, 2008, 2009 Red Hat Inc.
 
 This file is part of Cygwin.
 
@@ -23,6 +23,7 @@ void	setprogname (const char *);
 
 #ifndef __STRICT_ANSI__
 char *realpath (const char *, char *);
+char *canonicalize_file_name (const char *);
 int unsetenv (const char *);
 char *initstate (unsigned seed, char *state, size_t size);
 long random (void);

winsup/cygwin/include/cygwin/version.h

@@ -366,12 +366,13 @@ details. */
       210: New ctype layout using variable ctype pointer.  Export __ctype_ptr__.
       211: Export fpurge, mkstemps.
       212: Add and export libstdc++ malloc wrappers.
+      213: Export canonicalize_file_name, eaccess, euidaccess.
      */
 
      /* Note that we forgot to bump the api for ualarm, strtoll, strtoull */
 
 #define CYGWIN_VERSION_API_MAJOR 0
-#define CYGWIN_VERSION_API_MINOR 212
+#define CYGWIN_VERSION_API_MINOR 213
 
      /* There is also a compatibity version number associated with the
 	shared memory regions.  It is incremented when incompatible

winsup/cygwin/path.cc

@@ -2845,7 +2845,7 @@ cygwin_conv_to_full_posix_path (const char *path, char *posix_path)
 			   MAX_PATH);
 }
 
-/* The realpath function is supported on some UNIX systems.  */
+/* The realpath function is required by POSIX:2008.  */
 
 extern "C" char *
 realpath (const char *path, char *resolved)
@@ -2876,11 +2876,9 @@ realpath (const char *path, char *resolved)
   path_conv real_path (tpath, PC_SYM_FOLLOW | PC_POSIX, stat_suffixes);
 
 
-  /* Linux has this funny non-standard extension.  If "resolved" is NULL,
-     realpath mallocs the space by itself and returns it to the application.
-     The application is responsible for calling free() then.  This extension
-     is backed by POSIX, which allows implementation-defined behaviour if
-     "resolved" is NULL.  That's good enough for us to do the same here. */
+  /* POSIX 2008 requires malloc'ing if resolved is NULL, and states
+     that using non-NULL resolved is asking for portability
+     problems.  */
 
   if (!real_path.error && real_path.exists ())
     {
@@ -2894,14 +2892,24 @@ realpath (const char *path, char *resolved)
       return resolved;
     }
 
-  /* FIXME: on error, we are supposed to put the name of the path
-     component which could not be resolved into RESOLVED.  */
+  /* FIXME: on error, Linux puts the name of the path
+     component which could not be resolved into RESOLVED, but POSIX
+     does not require this.  */
   if (resolved)
     resolved[0] = '\0';
   set_errno (real_path.error ?: ENOENT);
   return NULL;
 }
 
+/* Linux provides this extension.  Since the only portable use of
+   realpath requires a NULL second argument, we might as well have a
+   one-argument wrapper.  */
+extern "C" char *
+canonicalize_file_name (const char *path)
+{
+  return realpath (path, NULL);
+}
+
 /* Return non-zero if path is a POSIX path list.
    This is exported to the world as cygwin_foo by cygwin.din.
 

winsup/cygwin/posix.sgml

@@ -890,6 +890,7 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008).</para>
     dn_expand
     dn_skipname
     drem
+    eaccess
     endusershell
     err
     errx
@@ -1005,6 +1006,7 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008).</para>
     asnprintf
     asprintf
     asprintf_r
+    canonicalize_file_name
     dremf
     envz_add
     envz_entry
@@ -1012,6 +1014,7 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008).</para>
     envz_merge
     envz_remove
     envz_strip
+    euidaccess
     exp10
     exp10f
     fcloseall

winsup/cygwin/syscalls.cc

@@ -1580,6 +1580,29 @@ access (const char *fn, int flags)
   return res;
 }
 
+/* Linux provides this extension; it is basically a wrapper around the
+   POSIX:2008 faccessat (AT_FDCWD, fn, flags, AT_EACCESS).  We also
+   provide eaccess as an alias for this, in cygwin.din.  */
+extern "C" int
+euidaccess (const char *fn, int flags)
+{
+  // flags were incorrectly specified
+  int res = -1;
+  if (flags & ~(F_OK|R_OK|W_OK|X_OK))
+    set_errno (EINVAL);
+  else
+    {
+      fhandler_base *fh = build_fh_name (fn, NULL, PC_SYM_FOLLOW, stat_suffixes);
+      if (fh)
+	{
+	  res =  fh->fhaccess (flags, true);
+	  delete fh;
+	}
+    }
+  debug_printf ("returning %d", res);
+  return res;
+}
+
 static void
 rename_append_suffix (path_conv &pc, const char *path, size_t len,
 		      const char *suffix)
@@ -3878,9 +3901,12 @@ fchmodat (int dirfd, const char *pathname, mode_t mode, int flags)
   myfault efault;
   if (efault.faulted (EFAULT))
     return -1;
-  if (flags & ~AT_SYMLINK_NOFOLLOW)
+  if (flags)
     {
-      set_errno (EINVAL);
+      /* BSD has lchmod, but Linux does not.  POSIX says
+	 AT_SYMLINK_NOFOLLOW is allowed to fail on symlinks; but Linux
+	 blindly fails even for non-symlinks.  */
+      set_errno ((flags & ~AT_SYMLINK_NOFOLLOW) ? EINVAL : EOPNOTSUPP);
       return -1;
     }
   char *path = tp.c_get ();