[PATCHv2 02/10] gdb: improve how 'remote exec-file' is stored and accessed

[Andrew Burgess <aburgess@redhat.com>]

This commit makes two related changes.  The goal of the commit is to
update the 'remote exec-file' setting to work correctly in a
multi-inferior setup.  To do this I have switched from the older
style add_setshow_* function, which uses a single backing variable, to
the newer style add_setshow_* functions that uses a get/set callback.

The get/set callbacks now directly access the state held in the
progspace which ensures that the correct value is always returned.

However, the new get/set API requires that the get callback return a
reference to the setting's value, which in this case needs to be a
std::string.

Currently the 'remote exec-file' setting is stored as a 'char *'
string, which isn't going to work.

And so, this commit also changes 'remote exec-file' to be stored as a
std::string within the progspace.

Now, when switching between multiple inferiors, GDB can correctly
inform the user about the value of the 'remote exec-file' setting.
---
 gdb/remote.c                             | 70 ++++++++++++------------
 gdb/testsuite/gdb.multi/gdb-settings.exp | 13 +++++
 2 files changed, 47 insertions(+), 36 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index bbe81ccb54f..8a3bb629837 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1223,7 +1223,7 @@ class remote_target : public process_stratum_target
   void remote_kill_k ();
 
   void extended_remote_disable_randomization (int val);
-  int extended_remote_run (const char *remote_exec_file,
+  int extended_remote_run (const std::string &remote_exec_file,
 			   const std::string &args);
 
   void send_environment_packet (const char *action,
@@ -1340,14 +1340,7 @@ is_remote_target (process_stratum_target *target)
 }
 
 /* Per-program-space data key.  */
-static const registry<program_space>::key<char, gdb::xfree_deleter<char>>
-  remote_pspace_data;
-
-/* The variable registered as the control variable used by the
-   remote exec-file commands.  While the remote exec-file setting is
-   per-program-space, the set/show machinery uses this as the 
-   location of the remote exec-file value.  */
-static std::string remote_exec_file_var;
+static const registry<program_space>::key<std::string> remote_pspace_data;
 
 /* The size to align memory write packets, when practical.  The protocol
    does not guarantee any alignment, and gdb will generate short
@@ -1669,47 +1662,50 @@ remote_target::get_remote_state ()
 
 /* Fetch the remote exec-file from the current program space.  */
 
-static const char *
+static const std::string &
 get_remote_exec_file (void)
 {
-  char *remote_exec_file;
-
-  remote_exec_file = remote_pspace_data.get (current_program_space);
-  if (remote_exec_file == NULL)
-    return "";
-
-  return remote_exec_file;
+  const std::string *remote_exec_file
+    = remote_pspace_data.get (current_program_space);
+  if (remote_exec_file == nullptr)
+    remote_exec_file = remote_pspace_data.emplace (current_program_space);
+  return *remote_exec_file;
 }
 
 /* Set the remote exec file for PSPACE.  */
 
 static void
 set_pspace_remote_exec_file (struct program_space *pspace,
-			     const char *remote_exec_file)
+			     const std::string &filename)
 {
-  char *old_file = remote_pspace_data.get (pspace);
-
-  xfree (old_file);
-  remote_pspace_data.set (pspace, xstrdup (remote_exec_file));
+  remote_pspace_data.clear (pspace);
+  remote_pspace_data.emplace (pspace, filename);
 }
 
-/* The "set/show remote exec-file" set command hook.  */
+/* The "set remote exec-file" callback.  */
 
 static void
-set_remote_exec_file (const char *ignored, int from_tty,
-		      struct cmd_list_element *c)
+set_remote_exec_file_cb (const std::string &filename)
 {
   set_pspace_remote_exec_file (current_program_space,
-			       remote_exec_file_var.c_str ());
+			       filename);
+}
+
+/* Get the value for the 'set remote exec-file' user setting.  */
+
+static const std::string &
+get_remote_exec_file_cb ()
+{
+  return get_remote_exec_file ();
 }
 
-/* The "set/show remote exec-file" show command hook.  */
+/* Implement the "show remote exec-file" command.  */
 
 static void
 show_remote_exec_file (struct ui_file *file, int from_tty,
 		       struct cmd_list_element *cmd, const char *value)
 {
-  gdb_printf (file, "%s\n", get_remote_exec_file ());
+  gdb_printf (file, "%s\n", get_remote_exec_file ().c_str ());
 }
 
 static int
@@ -10449,7 +10445,7 @@ remote_target::extended_remote_disable_randomization (int val)
 }
 
 int
-remote_target::extended_remote_run (const char *remote_exec_file,
+remote_target::extended_remote_run (const std::string &remote_exec_file,
 				    const std::string &args)
 {
   struct remote_state *rs = get_remote_state ();
@@ -10463,10 +10459,11 @@ remote_target::extended_remote_run (const char *remote_exec_file,
   strcpy (rs->buf.data (), "vRun;");
   len = strlen (rs->buf.data ());
 
-  if (strlen (remote_exec_file) * 2 + len >= get_remote_packet_size ())
+  if (remote_exec_file.size () * 2 + len >= get_remote_packet_size ())
     error (_("Remote file name too long for run packet"));
-  len += 2 * bin2hex ((gdb_byte *) remote_exec_file, rs->buf.data () + len,
-		      strlen (remote_exec_file));
+  len += 2 * bin2hex ((gdb_byte *) remote_exec_file.data (),
+		      rs->buf.data () + len,
+		      remote_exec_file.size ());
 
   if (!args.empty ())
     {
@@ -10501,7 +10498,7 @@ remote_target::extended_remote_run (const char *remote_exec_file,
 		 "try \"set remote exec-file\"?"));
       else
 	error (_("Running \"%s\" on the remote target failed"),
-	       remote_exec_file);
+	       remote_exec_file.c_str ());
     default:
       gdb_assert_not_reached ("bad switch");
     }
@@ -10618,7 +10615,7 @@ extended_remote_target::create_inferior (const char *exec_file,
   int run_worked;
   char *stop_reply;
   struct remote_state *rs = get_remote_state ();
-  const char *remote_exec_file = get_remote_exec_file ();
+  const std::string &remote_exec_file = get_remote_exec_file ();
 
   /* If running asynchronously, register the target file descriptor
      with the event loop.  */
@@ -15481,10 +15478,11 @@ Transfer files to and from the remote target system."),
 	   &remote_cmdlist);
 
   add_setshow_string_noescape_cmd ("exec-file", class_files,
-				   &remote_exec_file_var, _("\
+				   _("\
 Set the remote pathname for \"run\"."), _("\
 Show the remote pathname for \"run\"."), NULL,
-				   set_remote_exec_file,
+				   set_remote_exec_file_cb,
+				   get_remote_exec_file_cb,
 				   show_remote_exec_file,
 				   &remote_set_cmdlist,
 				   &remote_show_cmdlist);
diff --git a/gdb/testsuite/gdb.multi/gdb-settings.exp b/gdb/testsuite/gdb.multi/gdb-settings.exp
index 0ebd2bf2998..e5922221d47 100644
--- a/gdb/testsuite/gdb.multi/gdb-settings.exp
+++ b/gdb/testsuite/gdb.multi/gdb-settings.exp
@@ -71,6 +71,7 @@ foreach_with_prefix inf $inferiors {
     gdb_test_no_output "set args inf${inf}-args"
     gdb_test_no_output "set cwd /inf${inf}-cwd"
     gdb_test_no_output "set inferior-tty /inf${inf}-tty"
+    gdb_test_no_output "set remote exec-file /inf${inf}-remote-exec"
 }
 
 # Check settings are still correct for each inferior.
@@ -88,6 +89,9 @@ foreach_with_prefix inf $inferiors {
     gdb_test "with inferior-tty tmp-value -- print 1" " = 1"
     gdb_test "show inferior-tty" "/inf${inf}-tty.*"
 
+    gdb_test "with remote exec-file tmp-value -- print 1" " = 1"
+    gdb_test "show remote exec-file" "/inf${inf}-remote-exec"
+
     # If the inferiors are running check $_gdb_setting_str and
     # $_gdb_setting return the correct values.
     if { $run } {
@@ -101,6 +105,11 @@ foreach_with_prefix inf $inferiors {
 	    "\"/inf${inf}-tty\""
 	gdb_test {print $_gdb_setting("inferior-tty")} \
 	    "\"/inf${inf}-tty\""
+
+	gdb_test {print $_gdb_setting_str("remote exec-file")} \
+	    "\"/inf${inf}-remote-exec\""
+	gdb_test {print $_gdb_setting("remote exec-file")} \
+	    "\"/inf${inf}-remote-exec\""
     }
 
     # Check the settings can be read from Python.
@@ -109,6 +118,8 @@ foreach_with_prefix inf $inferiors {
 	gdb_test "python print(gdb.parameter('cwd'))" "/inf${inf}-cwd"
 	gdb_test "python print(gdb.parameter('inferior-tty'))" \
 	    "/inf${inf}-tty"
+	gdb_test "python print(gdb.parameter('remote exec-file'))" \
+	    "/inf${inf}-remote-exec"
     }
 
     # Check the settings can be read from Guile.
@@ -119,5 +130,7 @@ foreach_with_prefix inf $inferiors {
 	    "/inf${inf}-cwd"
 	gdb_test "guile (print (parameter-value \"inferior-tty\"))" \
 	    "/inf${inf}-tty"
+	gdb_test "guile (print (parameter-value \"remote exec-file\"))" \
+	    "/inf${inf}-remote-exec"
     }
 }
-- 
2.25.4