cli-script: use unique_ptr to not leak next struct

In cli/cli-script.c, process_next_line() allocates memory
which will eventually end up being assigned to the 'next'
field in struct command_line.  However, in a case
recurse_read_control_structure returns 'invalid_control'
this memory is leaked. This commit uses std::unique_ptr
as appropriate to prevent this leakage.

This issue was found by coverity scanning.

gdb/ChangeLog:

        * cli/cli-script.h (command_line_up): New unique_ptr typedef.
	* cli/cli-script.c (multi_line_command_p): Use unique_ptr
        command_line_up instead of struct command_line.
	(build_command_line): Likewise.
	(get_command_line): Update the cmd function call parameter.
	(process_next_line):  Use unique_ptr command_line_up instead
        of struct command_line.
	(recurse_read_control_structure): Change the the type of
        next to command_line_up.
	(read_command_lines_1): Change type of `next' to be
        command_line_up and update all references of `next'
        accordingly.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index de0fd2d6f105cdc6fefd98144e3da3d82664bf49..916b17e3951606feee3340eb33c3f174b0bafa8b 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,19 @@
+2021-05-20  Alexandra Hájková  <ahajkova@redhat.com>
+           Pedro Alves  <pedro@palves.net>
+
+       * cli/cli-script.h (command_line_up): New unique_ptr typedef.
+       * cli/cli-script.c (multi_line_command_p): Use unique_ptr
+       command_line_up instead of struct command_line.
+       (build_command_line): Likewise.
+       (get_command_line): Update the cmd function call parameter.
+       (process_next_line):  Use unique_ptr command_line_up instead
+       of struct command_line.
+       (recurse_read_control_structure): Change the the type of
+       next to command_line_up.
+       (read_command_lines_1): Change type of `next' to be
+       command_line_up and update all references of `next'
+       accordingly.
+
 2021-05-20  Alexandra Hájková  <ahajkova@redhat.com>
 
        * MAINTAINERS (Write After Approval): Add myself.

diff --git a/gdb/cli/cli-script.c b/gdb/cli/cli-script.c
index ff93523f4daae1bb463d503155ec7f34adcdb412..984636779023ac92abc5b87323281b8620beeac7 100644 (file)
--- a/gdb/cli/cli-script.c
+++ b/gdb/cli/cli-script.c
@@ -155,7 +155,7 @@ multi_line_command_p (enum command_control_type type)
 /* Allocate, initialize a new command line structure for one of the
    control commands (if/while).  */
 
-static struct command_line *
+static command_line_up
 build_command_line (enum command_control_type type, const char *args)
 {
   if (args == NULL || *args == '\0')
@@ -171,7 +171,7 @@ build_command_line (enum command_control_type type, const char *args)
     }
   gdb_assert (args != NULL);
 
-  return new struct command_line (type, xstrdup (args));
+  return command_line_up (new command_line (type, xstrdup (args)));
 }
 
 /* Build and return a new command structure for the control commands
@@ -181,7 +181,7 @@ counted_command_line
 get_command_line (enum command_control_type type, const char *arg)
 {
   /* Allocate and build a new command line structure.  */
-  counted_command_line cmd (build_command_line (type, arg),
+  counted_command_line cmd (build_command_line (type, arg).release (),
                            command_lines_deleter ());
 
   /* Read in the body of this command.  */
@@ -957,7 +957,7 @@ line_first_arg (const char *p)
    Otherwise, only "end" is recognized.  */
 
 static enum misc_command_type
-process_next_line (const char *p, struct command_line **command,
+process_next_line (const char *p, command_line_up *command,
                   int parse_commands,
                   gdb::function_view<void (const char *)> validator)
 
@@ -1055,9 +1055,9 @@ process_next_line (const char *p, struct command_line **command,
          *command = build_command_line (guile_control, "");
        }
       else if (p_end - p == 10 && startswith (p, "loop_break"))
-       *command = new struct command_line (break_control);
+       *command = command_line_up (new command_line (break_control));
       else if (p_end - p == 13 && startswith (p, "loop_continue"))
-       *command = new struct command_line (continue_control);
+       *command = command_line_up (new command_line (continue_control));
       else
        not_handled = 1;
     }
@@ -1065,22 +1065,12 @@ process_next_line (const char *p, struct command_line **command,
   if (!parse_commands || not_handled)
     {
       /* A normal command.  */
-      *command = new struct command_line (simple_control,
-                                         savestring (p, p_end - p));
+      *command = command_line_up (new command_line (simple_control,
+                                                   savestring (p, p_end - p)));
     }
 
   if (validator)
-    {
-      try
-       {
-         validator ((*command)->line);
-       }
-      catch (const gdb_exception &ex)
-       {
-         free_command_lines (command);
-         throw;
-       }
-    }
+    validator ((*command)->line);
 
   /* Nothing special.  */
   return ok_command;
@@ -1097,10 +1087,11 @@ recurse_read_control_structure (gdb::function_view<const char * ()> read_next_li
 {
   enum misc_command_type val;
   enum command_control_type ret;
-  struct command_line *child_tail, *next;
+  struct command_line *child_tail;
   counted_command_line *current_body = &current_cmd->body_list_0;
+  command_line_up next;
 
-  child_tail = NULL;
+  child_tail = nullptr;
 
   /* Sanity checks.  */
   if (current_cmd->control_type == simple_control)
@@ -1111,8 +1102,8 @@ recurse_read_control_structure (gdb::function_view<const char * ()> read_next_li
     {
       dont_repeat ();
 
-      next = NULL;
-      val = process_next_line (read_next_line_func (), &next, 
+      next = nullptr;
+      val = process_next_line (read_next_line_func (), &next,
                               current_cmd->control_type != python_control
                               && current_cmd->control_type != guile_control
                               && current_cmd->control_type != compile_control,
@@ -1144,7 +1135,7 @@ recurse_read_control_structure (gdb::function_view<const char * ()> read_next_li
              && current_body == &current_cmd->body_list_0)
            {
              current_body = &current_cmd->body_list_1;
-             child_tail = NULL;
+             child_tail = nullptr;
              continue;
            }
          else
@@ -1154,21 +1145,26 @@ recurse_read_control_structure (gdb::function_view<const char * ()> read_next_li
            }
        }
 
-      if (child_tail)
+      /* Transfer ownership of NEXT to the command's body list.  */
+      if (child_tail != nullptr)
        {
-         child_tail->next = next;
+         child_tail->next = next.release ();
+         child_tail = child_tail->next;
        }
       else
-       *current_body = counted_command_line (next, command_lines_deleter ());
-
-      child_tail = next;
+       {
+         child_tail = next.get ();
+         *current_body = counted_command_line (next.release (),
+                                               command_lines_deleter ());
+       }
 
       /* If the latest line is another control structure, then recurse
         on it.  */
-      if (multi_line_command_p (next->control_type))
+      if (multi_line_command_p (child_tail->control_type))
        {
          control_level++;
-         ret = recurse_read_control_structure (read_next_line_func, next,
+         ret = recurse_read_control_structure (read_next_line_func,
+                                               child_tail,
                                                validator);
          control_level--;
 
@@ -1240,10 +1236,11 @@ read_command_lines_1 (gdb::function_view<const char * ()> read_next_line_func,
                      int parse_commands,
                      gdb::function_view<void (const char *)> validator)
 {
-  struct command_line *tail, *next;
+  struct command_line *tail;
   counted_command_line head (nullptr, command_lines_deleter ());
   enum command_control_type ret;
   enum misc_command_type val;
+  command_line_up next;
 
   control_level = 0;
   tail = NULL;
@@ -1273,7 +1270,7 @@ read_command_lines_1 (gdb::function_view<const char * ()> read_next_line_func,
       if (multi_line_command_p (next->control_type))
        {
          control_level++;
-         ret = recurse_read_control_structure (read_next_line_func, next,
+         ret = recurse_read_control_structure (read_next_line_func, next.get (),
                                                validator);
          control_level--;
 
@@ -1281,15 +1278,18 @@ read_command_lines_1 (gdb::function_view<const char * ()> read_next_line_func,
            break;
        }
 
+      /* Transfer ownership of NEXT to the HEAD list.  */
       if (tail)
        {
-         tail->next = next;
+         tail->next = next.release ();
+         tail = tail->next;
        }
       else
        {
-         head = counted_command_line (next, command_lines_deleter ());
+         tail = next.get ();
+         head = counted_command_line (next.release (),
+                                      command_lines_deleter ());
        }
-      tail = next;
     }
 
   dont_repeat ();

diff --git a/gdb/cli/cli-script.h b/gdb/cli/cli-script.h
index 8624bf558392a52f53043ad3347632593e60a1ce..8c98fdde65563c76265dc2d79878208b8eabcd33 100644 (file)
--- a/gdb/cli/cli-script.h
+++ b/gdb/cli/cli-script.h
@@ -66,6 +66,9 @@ struct command_lines_deleter
 /* A reference-counted struct command_line.  */
 typedef std::shared_ptr<command_line> counted_command_line;
 
+/* A unique_ptr specialization for command_line.  */
+typedef std::unique_ptr<command_line, command_lines_deleter> command_line_up;
+
 /* * Structure for saved commands lines (for breakpoints, defined
    commands, etc).  */