gdb: make inferior::m_args an std::string

With the current code, both a NULL pointer and an empty string can mean
"no arguments".  We don't need this distinction.  Changing to a string
has the advantage that there is now a single state for that (an empty
string), which makes the code a bit simpler in my opinion.

Change-Id: Icdc622820f7869478791dbaa84b4a1c7fec21ced

gdb/elf-none-tdep.c

@@ -49,9 +49,9 @@ elf_none_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
       fname = lbasename (exe);
       psargs = std::string (exe);
 
-      const char *infargs = current_inferior ()->args ();
-      if (infargs != nullptr)
-	psargs += " " + std::string (infargs);
+      const std::string &infargs = current_inferior ()->args ();
+      if (!infargs.empty ())
+	psargs += ' ' + infargs;
 
       /* All existing targets that handle writing out prpsinfo expect the
 	 fname and psargs strings to be at least 16 and 80 characters long

gdb/fbsd-tdep.c

@@ -684,9 +684,9 @@ fbsd_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size)
       const char *fname = lbasename (get_exec_file (0));
       std::string psargs = fname;
 
-      const char *infargs = current_inferior ()->args ();
-      if (infargs != NULL)
-	psargs = psargs + " " + infargs;
+      const std::string &infargs = current_inferior ()->args ();
+      if (!infargs.empty ())
+	psargs += ' ' + infargs;
 
       note_data.reset (elfcore_write_prpsinfo (obfd, note_data.release (),
 					       note_size, fname,

gdb/infcmd.c

@@ -129,7 +129,7 @@ set_inferior_args_vector (int argc, char **argv)
 {
   gdb::array_view<char * const> args (argv, argc);
   std::string n = construct_inferior_arguments (args);
-  current_inferior ()->set_args (n.c_str ());
+  current_inferior ()->set_args (std::move (n));
 }
 
 /* Notice when `set args' is run.  */
@@ -151,7 +151,7 @@ show_args_command (struct ui_file *file, int from_tty,
   /* Note that we ignore the passed-in value in favor of computing it
      directly.  */
   deprecated_show_value_hack (file, from_tty, c,
-			      current_inferior ()->args ());
+			      current_inferior ()->args ().c_str ());
 }
 
 /* See gdbsupport/common-inferior.h.  */

gdb/inferior.h

@@ -444,26 +444,18 @@ public:
 
   /* Set the argument string to use when running this inferior.
 
-     Either nullptr or an empty string can be used to represent "no
-     arguments".  */
-  void set_args (const char *args)
+     An empty string can be used to represent "no arguments".  */
+  void set_args (std::string args)
   {
-    if (args != nullptr && args[0] != '\0')
-      m_args = make_unique_xstrdup (args);
-    else
-      m_args.reset ();
+    m_args = std::move (args);
   };
 
   /* Get the argument string to use when running this inferior.
 
-     The return value is always non-nullptr.  No arguments is represented by
-     an empty string.  */
-  const char *args () const
+     No arguments is represented by an empty string.  */
+  const std::string &args () const
   {
-    if (m_args == nullptr)
-      return "";
-
-    return m_args.get ();
+    return m_args;
   }
 
   /* Set the inferior current working directory.
@@ -602,10 +594,8 @@ private:
   /* The list of continuations.  */
   std::list<std::function<void ()>> m_continuations;
 
-  /* The arguments string to use when running.
-
-     This is nullptr when there are not args.  */
-  gdb::unique_xmalloc_ptr<char> m_args;
+  /* The arguments string to use when running.  */
+  std::string m_args;
 
   /* The current working directory that will be used when starting
      this inferior.  */

gdb/linux-tdep.c

@@ -1847,12 +1847,12 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
   strncpy (p->pr_fname, basename, sizeof (p->pr_fname) - 1);
   p->pr_fname[sizeof (p->pr_fname) - 1] = '\0';
 
-  const char *infargs = current_inferior ()->args ();
+  const std::string &infargs = current_inferior ()->args ();
 
   /* The arguments of the program.  */
   std::string psargs = fname.get ();
-  if (infargs != NULL)
-    psargs = psargs + " " + infargs;
+  if (!infargs.empty ())
+    psargs += ' ' + infargs;
 
   strncpy (p->pr_psargs, psargs.c_str (), sizeof (p->pr_psargs) - 1);
   p->pr_psargs[sizeof (p->pr_psargs) - 1] = '\0';

gdb/procfs.c

@@ -3603,7 +3603,6 @@ procfs_target::make_corefile_notes (bfd *obfd, int *note_size)
   char psargs[80] = {'\0'};
   procinfo *pi = find_procinfo_or_die (inferior_ptid.pid (), 0);
   gdb::unique_xmalloc_ptr<char> note_data;
-  const char *inf_args;
   enum gdb_signal stop_signal;
 
   if (get_exec_file (0))
@@ -3613,14 +3612,13 @@ procfs_target::make_corefile_notes (bfd *obfd, int *note_size)
       strncpy (psargs, get_exec_file (0), sizeof (psargs));
       psargs[sizeof (psargs) - 1] = 0;
 
-      inf_args = current_inferior ()->args ();
-      if (inf_args && *inf_args
-	  && (strlen (inf_args)
-	      < ((int) sizeof (psargs) - (int) strlen (psargs))))
+      const std::string &inf_args = current_inferior ()->args ();
+      if (!inf_args.empty () &&
+	  inf_args.length () < ((int) sizeof (psargs) - (int) strlen (psargs)))
 	{
 	  strncat (psargs, " ",
 		   sizeof (psargs) - strlen (psargs));
-	  strncat (psargs, inf_args,
+	  strncat (psargs, inf_args.c_str (),
 		   sizeof (psargs) - strlen (psargs));
 	}
     }