Add a --output=<DIR> option to ar to allow the specifying of an output directory.

	* ar.c (emum long option numbers): Declare.  Use to provide
	numerical values for long options.
	(long_options): Add --output option.
	(usage): Mention the --output option.
	(open_output_file): New function.  Create a filepath for an output
	file and open it.
	(extract_file): Use open_output_file().
	(open_output_file):
	* testsuite/binutils-all/ar.exp: Add a test of the new feature.
	* doc/binutils.texi: Document the new feature.
	* NEWS: Mention the new feature.

5 files changed, 171 insertions, 66 deletions

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index b723f569390..c85d93b9dce 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,18 @@
+2019-10-30  Fangrui Song  <i@maskray.me>
+	    Nick Clifton  <nickc@redhat.com>
+
+	* ar.c (emum long option numbers): Declare.  Use to provide
+	numerical values for long options.
+	(long_options): Add --output option.
+	(usage): Mention the --output option.
+	(open_output_file): New function.  Create a filepath for an output
+	file and open it.
+	(extract_file): Use open_output_file().
+	(open_output_file):
+	* testsuite/binutils-all/ar.exp: Add a test of the new feature.
+	* doc/binutils.texi: Document the new feature.
+	* NEWS: Mention the new feature.
+
 2019-10-26  Alan Modra  <amodra@gmail.com>
 
 	* objcopy.c (sort_gnu_build_notes): Correct sort of deleted
diff --git a/binutils/NEWS b/binutils/NEWS
index e6afc4ba29f..fd14d71ce92 100644
--- a/binutils/NEWS
+++ b/binutils/NEWS
@@ -1,5 +1,8 @@
 -*- text -*-
 
+* Add --output option to the "ar" program.  This option can be used to specify
+  the output directory when extracting members from an archive.
+
 Changes in 2.33:
 
 * Add --source-comment[=<txt>] option to objdump which if present,
diff --git a/binutils/ar.c b/binutils/ar.c
index 38c54c9fa8e..0af7954a47a 100644
--- a/binutils/ar.c
+++ b/binutils/ar.c
@@ -35,6 +35,7 @@
 #include "binemul.h"
 #include "plugin-api.h"
 #include "plugin.h"
+#include "ansidecl.h"
 
 #ifdef __GO32___
 #define EXT_NAME_LEN 3		/* Bufflen of addition to name if it's MS-DOS.  */
@@ -149,8 +150,14 @@ static const char *plugin_target = NULL;
 
 static const char *target = NULL;
 
-#define OPTION_PLUGIN 201
-#define OPTION_TARGET 202
+enum long_option_numbers
+{
+  OPTION_PLUGIN = 201,
+  OPTION_TARGET,
+  OPTION_OUTPUT
+};
+
+static const char * output_dir = NULL;
 
 static struct option long_options[] =
 {
@@ -158,6 +165,7 @@ static struct option long_options[] =
   {"plugin", required_argument, NULL, OPTION_PLUGIN},
   {"target", required_argument, NULL, OPTION_TARGET},
   {"version", no_argument, &show_version, 1},
+  {"output", required_argument, NULL, OPTION_OUTPUT},
   {NULL, no_argument, NULL, 0}
 };
 
@@ -327,6 +335,7 @@ usage (int help)
   fprintf (s, _("  [V]          - display the version number\n"));
   fprintf (s, _("  @<file>      - read options from <file>\n"));
   fprintf (s, _("  --target=BFDNAME - specify the target object format as BFDNAME\n"));
+  fprintf (s, _("  --output=DIRNAME - specify the output directory for extraction operations\n"));
 #if BFD_SUPPORTS_PLUGINS
   fprintf (s, _(" optional:\n"));
   fprintf (s, _("  --plugin <p> - load the specified plugin\n"));
@@ -592,6 +601,9 @@ decode_options (int argc, char **argv)
 	case OPTION_TARGET:
 	  target = optarg;
 	  break;
+	case OPTION_OUTPUT:
+	  output_dir = optarg;
+	  break;
 	case 0:		/* A long option that just sets a flag.  */
 	  break;
         default:
@@ -1050,6 +1062,49 @@ print_contents (bfd *abfd)
   free (cbuf);
 }
 
+
+static FILE * open_output_file (bfd *) ATTRIBUTE_RETURNS_NONNULL;
+
+static FILE *
+open_output_file (bfd * abfd)
+{
+  output_filename = bfd_get_filename (abfd);
+
+  if (output_dir)
+    {
+      size_t len = strlen (output_dir);
+
+      if (len > 0)
+	{
+	  /* FIXME: There is a memory leak here, but it is not serious.  */
+	  if (IS_DIR_SEPARATOR (output_dir [len - 1]))
+	    output_filename = concat (output_dir, output_filename, NULL);
+	  else
+	    output_filename = concat (output_dir, "/", output_filename, NULL);
+	}
+    }
+    
+  /* PR binutils/17533: Do not allow directory traversal
+     outside of the current directory tree.  */
+  if (! is_valid_archive_path (output_filename))
+    {
+      char * base = (char *) lbasename (output_filename);
+
+      non_fatal (_("illegal output pathname for archive member: %s, using '%s' instead"),
+		 output_filename, base);
+      output_filename = base;
+    }
+
+  FILE * ostream = fopen (output_filename, FOPEN_WB);
+  if (ostream == NULL)
+    {
+      perror (output_filename);
+      xexit (1);
+    }
+
+  return ostream;
+}
+
 /* Extract a member of the archive into its own file.
 
    We defer opening the new file until after we have read a BUFSIZ chunk of the
@@ -1063,23 +1118,9 @@ print_contents (bfd *abfd)
 void
 extract_file (bfd *abfd)
 {
-  FILE *ostream;
-  char *cbuf = (char *) xmalloc (BUFSIZE);
-  bfd_size_type nread, tocopy;
-  bfd_size_type ncopied = 0;
   bfd_size_type size;
   struct stat buf;
 
-  /* PR binutils/17533: Do not allow directory traversal
-     outside of the current directory tree.  */
-  if (! is_valid_archive_path (bfd_get_filename (abfd)))
-    {
-      non_fatal (_("illegal pathname found in archive member: %s"),
-		 bfd_get_filename (abfd));
-      free (cbuf);
-      return;
-    }
-
   if (bfd_stat_arch_elt (abfd, &buf) != 0)
     /* xgettext:c-format */
     fatal (_("internal stat error on %s"), bfd_get_filename (abfd));
@@ -1090,75 +1131,61 @@ extract_file (bfd *abfd)
 
   bfd_seek (abfd, (file_ptr) 0, SEEK_SET);
 
-  ostream = NULL;
+  output_file = NULL;
   if (size == 0)
     {
-      /* Seems like an abstraction violation, eh?  Well it's OK! */
-      output_filename = bfd_get_filename (abfd);
+      output_file = open_output_file (abfd);
+    }
+  else
+    {
+      bfd_size_type ncopied = 0;
+      char *cbuf = (char *) xmalloc (BUFSIZE);
 
-      ostream = fopen (bfd_get_filename (abfd), FOPEN_WB);
-      if (ostream == NULL)
+      while (ncopied < size)
 	{
-	  perror (bfd_get_filename (abfd));
-	  xexit (1);
-	}
+	  bfd_size_type nread, tocopy;
 
-      output_file = ostream;
-    }
-  else
-    while (ncopied < size)
-      {
-	tocopy = size - ncopied;
-	if (tocopy > BUFSIZE)
-	  tocopy = BUFSIZE;
-
-	nread = bfd_bread (cbuf, tocopy, abfd);
-	if (nread != tocopy)
-	  /* xgettext:c-format */
-	  fatal (_("%s is not a valid archive"),
-		 bfd_get_filename (abfd->my_archive));
+	  tocopy = size - ncopied;
+	  if (tocopy > BUFSIZE)
+	    tocopy = BUFSIZE;
 
-	/* See comment above; this saves disk arm motion */
-	if (ostream == NULL)
-	  {
-	    /* Seems like an abstraction violation, eh?  Well it's OK! */
-	    output_filename = bfd_get_filename (abfd);
+	  nread = bfd_bread (cbuf, tocopy, abfd);
+	  if (nread != tocopy)
+	    /* xgettext:c-format */
+	    fatal (_("%s is not a valid archive"),
+		   bfd_get_filename (abfd->my_archive));
 
-	    ostream = fopen (bfd_get_filename (abfd), FOPEN_WB);
-	    if (ostream == NULL)
-	      {
-		perror (bfd_get_filename (abfd));
-		xexit (1);
-	      }
+	  /* See comment above; this saves disk arm motion.  */
+	  if (output_file == NULL)
+	    output_file = open_output_file (abfd);
 
-	    output_file = ostream;
-	  }
+	  /* fwrite in mingw32 may return int instead of bfd_size_type. Cast
+	     the return value to bfd_size_type to avoid comparison between
+	     signed and unsigned values.  */
+	  if ((bfd_size_type) fwrite (cbuf, 1, nread, output_file) != nread)
+	    fatal ("%s: %s", output_filename, strerror (errno));
 
-	/* fwrite in mingw32 may return int instead of bfd_size_type. Cast
-	   the return value to bfd_size_type to avoid comparison between
-	   signed and unsigned values.  */
-	if ((bfd_size_type) fwrite (cbuf, 1, nread, ostream) != nread)
-	  fatal ("%s: %s", output_filename, strerror (errno));
-	ncopied += tocopy;
-      }
+	  ncopied += tocopy;
+	}
 
-  if (ostream != NULL)
-    fclose (ostream);
+      free (cbuf);
+    }
+
+  fclose (output_file);
 
   output_file = NULL;
-  output_filename = NULL;
 
-  chmod (bfd_get_filename (abfd), buf.st_mode);
+  chmod (output_filename, buf.st_mode);
 
   if (preserve_dates)
     {
       /* Set access time to modification time.  Only st_mtime is
 	 initialized by bfd_stat_arch_elt.  */
       buf.st_atime = buf.st_mtime;
-      set_times (bfd_get_filename (abfd), &buf);
+      set_times (output_filename, &buf);
     }
 
-  free (cbuf);
+  output_filename = NULL;
 }
 
 static void
diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
index 2edd7e1aa10..97abf980ba8 100644
--- a/binutils/doc/binutils.texi
+++ b/binutils/doc/binutils.texi
@@ -169,7 +169,7 @@ in the section entitled ``GNU Free Documentation License''.
 @c man title ar create, modify, and extract from archives
 
 @smallexample
-ar [-]@var{p}[@var{mod}] [@option{--plugin} @var{name}] [@option{--target} @var{bfdname}] [@var{relpos}] [@var{count}] @var{archive} [@var{member}@dots{}]
+ar [-]@var{p}[@var{mod}] [@option{--plugin} @var{name}] [@option{--target} @var{bfdname}] [@option{--output} @var{dirname}] [@var{relpos}] [@var{count}] @var{archive} [@var{member}@dots{}]
 ar -M [ <mri-script ]
 @end smallexample
 
@@ -253,7 +253,7 @@ program.
 
 @smallexample
 @c man begin SYNOPSIS ar
-ar [@option{-X32_64}] [@option{-}]@var{p}[@var{mod}] [@option{--plugin} @var{name}] [@option{--target} @var{bfdname}] [@var{relpos}] [@var{count}] @var{archive} [@var{member}@dots{}]
+ar [@option{-X32_64}] [@option{-}]@var{p}[@var{mod}] [@option{--plugin} @var{name}] [@option{--target} @var{bfdname}] [@option{--output} @var{dirname}] [@var{relpos}] [@var{count}] @var{archive} [@var{member}@dots{}]
 @c man end
 @end smallexample
 
@@ -579,6 +579,21 @@ The optional command-line switch @option{--target @var{bfdname}}
 specifies that the archive members are in an object code format
 different from your system's default format.  See
 @xref{Target Selection}, for more information.
+
+@item --output @var{dirname}
+The @option{--output} option can be used to specify a path to a
+directory into which archive members should be extracted.  If this
+option is not specified then the current directory will be used.
+
+Note - although the presence of this option does imply a @option{x} 
+extraction operation that option must still be included on the command
+line.
+
+Note - using this option does not allow archive members to be
+extracted to locations outside of the current directory, or one of its 
+sub-directories.  This is a security feature to prevent archives
+created with the @option{P} option from maliciously overwriting user
+files.
 @end table
 @c man end
 
diff --git a/binutils/testsuite/binutils-all/ar.exp b/binutils/testsuite/binutils-all/ar.exp
index bc1fbdb3cc4..c043f7e5508 100644
--- a/binutils/testsuite/binutils-all/ar.exp
+++ b/binutils/testsuite/binutils-all/ar.exp
@@ -605,6 +605,50 @@ proc empty_archive { } {
     pass $testname
 }
 
+# Test extracting an element.
+
+proc extract_an_element { } {
+    global AR
+    global AS
+    global srcdir
+    global subdir
+
+    set testname "ar extracting an element"
+
+    if ![binutils_assemble $srcdir/$subdir/bintest.s tmpdir/bintest.o] {
+	unresolved $testname
+	return
+    }
+
+    set archive artest.a
+
+    if [is_remote host] {
+	set objfile [remote_download host tmpdir/bintest.o]
+	remote_file host delete $archive
+    } else {
+	set objfile tmpdir/bintest.o
+    }
+
+    remote_file build delete $archive
+
+    set got [binutils_run $AR "-r -c $archive ${objfile}"]
+    if ![string match "" $got] {
+	fail $testname
+	return
+    }
+
+    set got [binutils_run $AR "--output=tmpdir -x $archive ${objfile}"]
+    if ![string match "" $got] {
+	fail $testname
+	return
+    }
+
+    remote_file build delete $archive
+    remote_file build delete tmpdir/$archive
+
+    pass $testname
+}
+
 # Run the tests.
 
 # Only run the bfdtest checks if the programs exist.  Since these
@@ -625,6 +669,7 @@ deterministic_archive
 delete_an_element
 move_an_element
 empty_archive
+extract_an_element
 
 if { [is_elf_format] && [supports_gnu_unique] } {
     unique_symbol