Support an "unlimited" number of user-defined argumentsusers/palves/cxx-eliminate-cleanups-v2

I recently wrote a user-defined command that would benefit from
supporting an unlimited number of arguments:

 http://palves.net/list-active-signal-handlers-with-gdb/

However, we currently only support up to 10 arguments passed to
user-defined commands ($arg0..$arg9).

I can't find a good reason for that, other than "old code with hard
coded limits".  This patch removes that limit and modernizes the code
along the way:

  - Makes the user_args struct a real C++ class that uses std::vector
    for storage.

  - Removes the "next" pointer from within user_args and uses a
    std::vector to maintain a stack instead.

  - Adds a new RAII-based scoped_user_args_level class to help
    push/pop user args in the stack instead of using a cleanup.

I also needed a way to convert a number to a std::string, so I added a
new utility for that, gdb::to_string.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention that user commands now accept an unlimited number
	of arguments.
	* cli/cli-script.c: Include <vector>.
	(struct string_view): New type.
	(MAXUSERARGS): Delete.
	(struct user_args): Now a C++ class.
	(user_args_stack): New.
	(struct scoped_user_args_level): New type.
	(execute_user_command): Use scoped_user_args_level.  Adjust to
	call insert_user_args instead of insert_args.
	(arg_cleanup): Delete.
	(setup_user_args): Deleted, and refactored as ...
	(user_args::user_args): ... this new constructor.  Limit of number
	of arguments removed.
	(insert_args): Delete.
	(insert_user_args) New.
	(user_args::insert_args): New, bits based on old insert_args with
	limit of number of arguments eliminated.
	* common/common-utils.h: Include <sstream>.
	(gdb::to_string): New.

gdb/doc/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (User-defined Commands): Limit on number of
	arguments passed to user-defined commands removed; update.

4 files changed, 135 insertions, 92 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index 4a614388566..2317dd82099 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -17,6 +17,9 @@
 
 * Support for Java programs compiled with gcj has been removed.
 
+* User commands now accept an unlimited number of arguments.
+  Previously, only up to 10 was accepted.
+
 * New targets
 
 Synopsys ARC			arc*-*-elf32
diff --git a/gdb/cli/cli-script.c b/gdb/cli/cli-script.c
index 6302f524070..a0b9a0ddac4 100644
--- a/gdb/cli/cli-script.c
+++ b/gdb/cli/cli-script.c
@@ -33,6 +33,8 @@
 #include "interps.h"
 #include "compile/compile.h"
 
+#include <vector>
+
 /* Prototypes for local functions.  */
 
 static enum command_control_type
@@ -41,9 +43,7 @@ recurse_read_control_structure (char * (*read_next_line_func) (void),
 				void (*validator)(char *, void *),
 				void *closure);
 
-static std::string insert_args (const char *line);
-
-static struct cleanup * setup_user_args (char *p);
+static std::string insert_user_args (const char *line);
 
 static char *read_next_line (void);
 
@@ -56,24 +56,69 @@ static int command_nest_depth = 1;
 /* This is to prevent certain commands being printed twice.  */
 static int suppress_next_print_command_trace = 0;
 
+/* A non-owning slice of a string.  */
+
+struct string_view
+{
+  string_view (const char *str_, size_t len_)
+    : str (str_), len (len_)
+  {}
+
+  const char *str;
+  size_t len;
+};
+
 /* Structure for arguments to user defined functions.  */
-#define MAXUSERARGS 10
-struct user_args
+
+class user_args
+{
+public:
+  /* Save the command line and store the locations of arguments passed
+     to the user defined function.  */
+  explicit user_args (const char *line);
+
+  /* Insert the stored user defined arguments into the $arg arguments
+     found in line.  */
+  std::string insert_args (const char *line);
+
+private:
+  /* Disable copy/assignment.  (Since the elements of A points inside
+     COMMAND, copying would need to reconstruct the A vector in the
+     new copy.)  */
+  user_args (const user_args &);
+  user_args &operator= (const user_args &);
+
+  /* It is necessary to store a copy of the command line to ensure
+     that the arguments are not overwritten before they are used.  */
+  std::string m_command_line;
+
+  /* The arguments.  Each element points inside M_COMMAND_LINE.  */
+  std::vector<string_view> m_args;
+};
+
+/* The stack of arguments passed to user defined functions.  We need a
+   stack because user-defined functions can call other user-defined
+   functions.  The vector owns its elements.  */
+static std::vector<user_args *> user_args_stack;
+
+/* An RAII-base class used to push/pop args on the user args
+   stack.  */
+struct scoped_user_args_level
+{
+  /* Parse the command line and push the arguments in the user args
+     stack.  */
+  explicit scoped_user_args_level (const char *line)
   {
-    struct user_args *next;
-    /* It is necessary to store a malloced copy of the command line to
-       ensure that the arguments are not overwritten before they are
-       used.  */
-    char *command;
-    struct
-      {
-	char *arg;
-	int len;
-      }
-    a[MAXUSERARGS];
-    int count;
+    user_args_stack.push_back (new user_args (line));
   }
- *user_args;
+
+  /* Pop the current user arguments from the stack.  */
+  ~scoped_user_args_level ()
+  {
+    delete user_args_stack.back ();
+    user_args_stack.pop_back ();
+  }
+};
 
 
 /* Return non-zero if TYPE is a multi-line command (i.e., is terminated
@@ -348,7 +393,6 @@ do_restore_user_call_depth (void * call_depth)
     in_user_command = 0;
 }
 
-
 void
 execute_user_command (struct cmd_list_element *c, char *args)
 {
@@ -364,12 +408,12 @@ execute_user_command (struct cmd_list_element *c, char *args)
     /* Null command */
     return;
 
-  old_chain = setup_user_args (args);
+  scoped_user_args_level push_user_args (args);
 
   if (++user_call_depth > max_user_call_depth)
     error (_("Max user call depth exceeded -- command aborted."));
 
-  make_cleanup (do_restore_user_call_depth, &user_call_depth);
+  old_chain = make_cleanup (do_restore_user_call_depth, &user_call_depth);
 
   /* Set the instream to 0, indicating execution of a
      user-defined function.  */
@@ -456,7 +500,7 @@ execute_control_command (struct command_line *cmd)
     case simple_control:
       {
 	/* A simple command, execute it and return.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_args (cmd->line);
 	execute_command (&new_line[0], 0);
 	ret = cmd->control_type;
 	break;
@@ -487,7 +531,7 @@ execute_control_command (struct command_line *cmd)
 	print_command_trace (buffer);
 
 	/* Parse the loop control expression for the while statement.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_args (cmd->line);
 	expression_up expr = parse_expression (new_line.c_str ());
 
 	ret = simple_control;
@@ -552,7 +596,7 @@ execute_control_command (struct command_line *cmd)
 	print_command_trace (buffer);
 
 	/* Parse the conditional for the if statement.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_args (cmd->line);
 	expression_up expr = parse_expression (new_line.c_str ());
 
 	current = NULL;
@@ -592,7 +636,7 @@ execute_control_command (struct command_line *cmd)
       {
 	/* Breakpoint commands list, record the commands in the
 	   breakpoint's command list and return.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_args (cmd->line);
 	ret = commands_from_control_command (new_line.c_str (), cmd);
 	break;
       }
@@ -678,62 +722,32 @@ if_command (char *arg, int from_tty)
   do_cleanups (old_chain);
 }
 
-/* Cleanup */
-static void
-arg_cleanup (void *ignore)
-{
-  struct user_args *oargs = user_args;
-
-  if (!user_args)
-    internal_error (__FILE__, __LINE__,
-		    _("arg_cleanup called with no user args.\n"));
-
-  user_args = user_args->next;
-  xfree (oargs->command);
-  xfree (oargs);
-}
-
-/* Bind the incomming arguments for a user defined command to
-   $arg0, $arg1 ... $argMAXUSERARGS.  */
+/* Bind the incoming arguments for a user defined command to $arg0,
+   $arg1 ... $argN.  */
 
-static struct cleanup *
-setup_user_args (char *p)
+user_args::user_args (const char *command_line)
 {
-  struct user_args *args;
-  struct cleanup *old_chain;
-  unsigned int arg_count = 0;
-
-  args = XNEW (struct user_args);
-  memset (args, 0, sizeof (struct user_args));
-
-  args->next = user_args;
-  user_args = args;
-
-  old_chain = make_cleanup (arg_cleanup, 0/*ignored*/);
+  const char *p;
 
-  if (p == NULL)
-    return old_chain;
+  if (command_line == NULL)
+    return;
 
-  user_args->command = p = xstrdup (p);
+  m_command_line = command_line;
+  p = m_command_line.c_str ();
 
   while (*p)
     {
-      char *start_arg;
+      const char *start_arg;
       int squote = 0;
       int dquote = 0;
       int bsquote = 0;
 
-      if (arg_count >= MAXUSERARGS)
-	error (_("user defined function may only have %d arguments."),
-	       MAXUSERARGS);
-
       /* Strip whitespace.  */
       while (*p == ' ' || *p == '\t')
 	p++;
 
       /* P now points to an argument.  */
       start_arg = p;
-      user_args->a[arg_count].arg = p;
 
       /* Get to the end of this argument.  */
       while (*p)
@@ -767,11 +781,8 @@ setup_user_args (char *p)
 	    }
 	}
 
-      user_args->a[arg_count].len = p - start_arg;
-      arg_count++;
-      user_args->count++;
+      m_args.push_back (string_view (start_arg, p - start_arg));
     }
-  return old_chain;
 }
 
 /* Given character string P, return a point to the first argument
@@ -790,48 +801,59 @@ locate_arg (const char *p)
   return NULL;
 }
 
-/* Insert the user defined arguments stored in user_arg into the $arg
-   arguments found in line.  */
+/* Insert the user defined arguments stored at top of the user args
+   stack into the $arg arguments found in line.  */
 
 static std::string
-insert_args (const char *line)
+insert_user_args (const char *line)
 {
   /* If we are not in a user-defined function, treat $argc, $arg0, et
      cetera as normal convenience variables.  */
-  if (user_args == NULL)
+  if (user_args_stack.empty ())
     return line;
 
+  user_args *args = user_args_stack.back ();
+  return args->insert_args (line);
+}
+
+/* Insert the user defined arguments stored in user_arg into the $arg
+   arguments found in line.  */
+
+std::string
+user_args::insert_args (const char *line)
+{
   std::string new_line;
   const char *p;
 
   while ((p = locate_arg (line)))
     {
-      int i, len;
-
       new_line.append (line, p - line);
 
       if (p[4] == 'c')
 	{
-	  gdb_assert (user_args->count >= 0 && user_args->count <= 10);
-	  if (user_args->count == 10)
-	    {
-	      new_line += '1';
-	      new_line += '0';
-	    }
-	  else
-	    new_line += user_args->count + '0';
+	  new_line += gdb::to_string (m_args.size ());
+	  line = p + 5;
 	}
       else
 	{
-	  i = p[4] - '0';
-	  if (i >= user_args->count)
-	    error (_("Missing argument %d in user function."), i);
+	  char *tmp;
+	  unsigned long i;
 
-	  len = user_args->a[i].len;
-	  if (len > 0)
-	    new_line.append (user_args->a[i].arg, len);
+	  errno = 0;
+	  i = strtoul (p + 4, &tmp, 10);
+	  if ((i == 0 && tmp == p + 4) || errno != 0)
+	    {
+	      line = p + 4;
+	    }
+	  else if (i >= m_args.size ())
+	    error (_("Missing argument %ld in user function."), i);
+	  else
+	    {
+	      new_line.append (m_args[i].str, m_args[i].len);
+
+	      line = tmp;
+	    }
 	}
-      line = p + 5;
     }
   /* Don't forget the tail.  */
   new_line.append (line);
diff --git a/gdb/common/common-utils.h b/gdb/common/common-utils.h
index a9053ffa48d..13592defb5d 100644
--- a/gdb/common/common-utils.h
+++ b/gdb/common/common-utils.h
@@ -21,6 +21,7 @@
 #define COMMON_UTILS_H
 
 #include <string>
+#include <sstream>
 
 /* If possible, define FUNCTION_NAME, a macro containing the name of
    the function being defined.  Since this macro may not always be
@@ -62,6 +63,23 @@ int xsnprintf (char *str, size_t size, const char *format, ...)
 std::string string_printf (const char* fmt, ...)
   ATTRIBUTE_PRINTF (1, 2);
 
+/* Returns a string representation of val.  Replacement for
+   std::to_string, which is only available in C++11 or later.  */
+
+namespace gdb {
+
+template <class T>
+inline std::string
+to_string (const T &val)
+{
+  std::stringstream ss;
+
+  ss << val;
+  return ss.str ();
+}
+
+}
+
 /* Make a copy of the string at PTR with LEN characters
    (and add a null character at the end in the copy).
    Uses malloc to get the space.  Returns the address of the copy.  */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index b3eb4885cf5..4d48469f584 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -24057,9 +24057,9 @@ files.
 @cindex arguments, to user-defined commands
 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
 which you assign a new name as a command.  This is done with the
-@code{define} command.  User commands may accept up to 10 arguments
+@code{define} command.  User commands may accept an unlimited number of arguments
 separated by whitespace.  Arguments are accessed within the user command
-via @code{$arg0@dots{}$arg9}.  A trivial example:
+via @code{$arg0@dots{}$argN}.  A trivial example:
 
 @smallexample
 define adder
@@ -24083,7 +24083,7 @@ functions calls.
 @cindex argument count in user-defined commands
 @cindex how many arguments (user-defined commands)
 In addition, @code{$argc} may be used to find out how many arguments have
-been passed.  This expands to a number in the range 0@dots{}10.
+been passed.
 
 @smallexample
 define adder