Change gdb_realpath to return a unique_xmalloc_ptr

This changes gdb_realpath to return a unique_xmalloc_ptr and fixes up
the callers.  This allows removing some cleanups.  This change by
itself caused xfullpath.exp to fail; and attempting to fix that ran
into various problems (like .get() being optimized out); so this patch
also rewrites xfullpath.exp to be a C++ selftest instead.

ChangeLog
2017-08-22  Tom Tromey  <tom@tromey.com>

	* exec.c (exec_file_attach): Update.
	* linux-thread-db.c (try_thread_db_load): Update.
	* guile/scm-safe-call.c (gdbscm_safe_source_script): Update.
	* utils.c (gdb_realpath): Change return type.
	(gdb_realpath_keepfile): Update.
	(gdb_realpath_check_trailer, gdb_realpath_tests): New functions.
	(_initialize_utils): Register the new self test.
	* source.c (openp): Update.
	(find_and_open_source): Update.
	* nto-tdep.c (nto_find_and_open_solib): Update.
	* main.c (set_gdb_data_directory): Update.
	(captured_main_1): Update.
	* dwarf2read.c (dwarf2_get_dwz_file): Update
	(dw2_map_symbol_filenames): Update.
	* auto-load.c (auto_load_safe_path_vec_update): Update.
	(filename_is_in_auto_load_safe_path_vec): Change type of
	"filename_realp".
	(auto_load_objfile_script): Update.
	(file_is_auto_load_safe): Update.  Use std::string.
	* utils.h (gdb_realpath): Return a gdb::unique_xmalloc_ptr.

testsuite/ChangeLog
2017-08-22  Tom Tromey  <tom@tromey.com>

	* gdb.gdb/xfullpath.exp: Remove.

1 files changed, 11 insertions, 16 deletions

diff --git a/gdb/exec.c b/gdb/exec.c
index 45bc133..92c87e4 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -249,16 +249,12 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
 void
 exec_file_attach (const char *filename, int from_tty)
 {
-  struct cleanup *cleanups;
-
   /* First, acquire a reference to the current exec_bfd.  We release
      this at the end of the function; but acquiring it now lets the
      BFD cache return it if this call refers to the same file.  */
   gdb_bfd_ref (exec_bfd);
   gdb_bfd_ref_ptr exec_bfd_holder (exec_bfd);
 
-  cleanups = make_cleanup (null_cleanup, NULL);
-
   /* Remove any previous exec file.  */
   exec_close ();
 
@@ -274,7 +270,7 @@ exec_file_attach (const char *filename, int from_tty)
   else
     {
       int load_via_target = 0;
-      char *scratch_pathname, *canonical_pathname;
+      const char *scratch_pathname, *canonical_pathname;
       int scratch_chan;
       struct target_section *sections = NULL, *sections_end = NULL;
       char **matching;
@@ -287,6 +283,7 @@ exec_file_attach (const char *filename, int from_tty)
 	    load_via_target = 1;
 	}
 
+      gdb::unique_xmalloc_ptr<char> canonical_storage, scratch_storage;
       if (load_via_target)
 	{
 	  /* gdb_bfd_fopen does not support "target:" filenames.  */
@@ -295,19 +292,18 @@ exec_file_attach (const char *filename, int from_tty)
 		       "not supported for %s sysroots"),
 		     TARGET_SYSROOT_PREFIX);
 
-	  scratch_pathname = xstrdup (filename);
-	  make_cleanup (xfree, scratch_pathname);
-
+	  scratch_pathname = filename;
 	  scratch_chan = -1;
-
 	  canonical_pathname = scratch_pathname;
 	}
       else
 	{
+	  char *temp_pathname;
+
 	  scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST,
 				filename, write_files ?
 				O_RDWR | O_BINARY : O_RDONLY | O_BINARY,
-				&scratch_pathname);
+				&temp_pathname);
 #if defined(__GO32__) || defined(_WIN32) || defined(__CYGWIN__)
 	  if (scratch_chan < 0)
 	    {
@@ -318,18 +314,19 @@ exec_file_attach (const char *filename, int from_tty)
 				    exename, write_files ?
 				    O_RDWR | O_BINARY
 				    : O_RDONLY | O_BINARY,
-				    &scratch_pathname);
+				    &temp_pathname);
 	    }
 #endif
 	  if (scratch_chan < 0)
 	    perror_with_name (filename);
 
-	  make_cleanup (xfree, scratch_pathname);
+	  scratch_storage.reset (temp_pathname);
+	  scratch_pathname = temp_pathname;
 
 	  /* gdb_bfd_open (and its variants) prefers canonicalized
 	     pathname for better BFD caching.  */
-	  canonical_pathname = gdb_realpath (scratch_pathname);
-	  make_cleanup (xfree, canonical_pathname);
+	  canonical_storage = gdb_realpath (scratch_pathname);
+	  canonical_pathname = canonical_storage.get ();
 	}
 
       gdb_bfd_ref_ptr temp;
@@ -390,8 +387,6 @@ exec_file_attach (const char *filename, int from_tty)
 	(*deprecated_exec_file_display_hook) (filename);
     }
 
-  do_cleanups (cleanups);
-
   bfd_cache_close_all ();
   observer_notify_executable_changed ();
 }