libiberty: Expose choose_tmpdir, and fix constness of return type

include/ChangeLog:
	* libiberty.h (choose_tmpdir): New prototype.

libiberty/ChangeLog:
	* choose-temp.c (choose_tmpdir): Remove now-redundant local
	copy of prototype.
	* functions.texi: Regenerate.
	* make-temp-file.c (choose_tmpdir): Convert return type from
	char * to const char * - given that this returns a pointer to
	a memoized allocation, the caller must not touch it.

From-SVN: r216285

include/ChangeLog

@@ -1,3 +1,7 @@
+2014-10-15  David Malcolm  <dmalcolm@redhat.com>
+
+	* libiberty.h (choose_tmpdir): New prototype.
+
 2013-10-02  Mark Wielaard  <mjw@redhat.com>
 
 	PR debug/63239

include/libiberty.h

@@ -227,6 +227,11 @@ extern char *make_relative_prefix (const char *, const char *,
 extern char *make_relative_prefix_ignore_links (const char *, const char *,
 						const char *) ATTRIBUTE_MALLOC;
 
+/* Returns a pointer to a directory path suitable for creating temporary
+   files in.  */
+
+extern const char *choose_tmpdir (void) ATTRIBUTE_RETURNS_NONNULL;
+
 /* Choose a temporary directory to use for scratch files.  */
 
 extern char *choose_temp_base (void) ATTRIBUTE_MALLOC ATTRIBUTE_RETURNS_NONNULL;

libiberty/ChangeLog

@@ -1,3 +1,12 @@
+2014-10-15  David Malcolm  <dmalcolm@redhat.com>
+
+	* choose-temp.c (choose_tmpdir): Remove now-redundant local
+	copy of prototype.
+	* functions.texi: Regenerate.
+	* make-temp-file.c (choose_tmpdir): Convert return type from
+	char * to const char * - given that this returns a pointer to
+	a memoized allocation, the caller must not touch it.
+
 2014-10-14  Joel Brobecker  <brobecker@adacore.com>
 
 	* d-demangle.c: Replace strtold with strtod in global comment.

libiberty/choose-temp.c

@@ -34,7 +34,6 @@ Boston, MA 02110-1301, USA.  */
 #endif
 
 #include "libiberty.h"
-extern char *choose_tmpdir (void);
 
 /* Name of temporary file.
    mktemp requires 6 trailing X's.  */

libiberty/functions.texi

@@ -125,7 +125,7 @@ Uses @code{malloc} to allocate storage for @var{nelem} objects of
 
 @end deftypefn
 
-@c choose-temp.c:46
+@c choose-temp.c:45
 @deftypefn Extension char* choose_temp_base (void)
 
 Return a prefix for temporary file names or @code{NULL} if unable to
@@ -139,7 +139,7 @@ not recommended.
 @end deftypefn
 
 @c make-temp-file.c:96
-@deftypefn Replacement char* choose_tmpdir ()
+@deftypefn Replacement const char* choose_tmpdir ()
 
 Returns a pointer to a directory path suitable for creating temporary
 files in.
@@ -160,9 +160,8 @@ number of seconds used.
   @dots{}, @code{NULL})
 
 Concatenate zero or more of strings and return the result in freshly
-@code{xmalloc}ed memory.  Returns @code{NULL} if insufficient memory is
+@code{xmalloc}ed memory.  The argument list is terminated by the first
-available.  The argument list is terminated by the first @code{NULL}
+@code{NULL} pointer encountered.  Pointers to empty strings are ignored.
-pointer encountered.  Pointers to empty strings are ignored.
 
 @end deftypefn
 
@@ -528,7 +527,7 @@ nineteen EBCDIC varying characters is tested; exercise caution.)
 @end ftable
 @end defvr
 
-@c hashtab.c:336
+@c hashtab.c:328
 @deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @
 htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @
 htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @
@@ -1163,7 +1162,7 @@ control over the state of the random number generator.
 
 @end deftypefn
 
-@c concat.c:174
+@c concat.c:160
 @deftypefn Extension char* reconcat (char *@var{optr}, const char *@var{s1}, @
   @dots{}, @code{NULL})
 

libiberty/make-temp-file.c

@@ -93,7 +93,7 @@ static char *memoized_tmpdir;
 
 /*
 
-@deftypefn Replacement char* choose_tmpdir ()
+@deftypefn Replacement const char* choose_tmpdir ()
 
 Returns a pointer to a directory path suitable for creating temporary
 files in.
@@ -102,7 +102,7 @@ files in.
 
 */
 
-char *
+const char *
 choose_tmpdir (void)
 {
   if (!memoized_tmpdir)