[PATCH v2 31/31] Support an "unlimited" number of user-defined arguments

Pedro Alves
2016-10-19T01:13:28Z

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

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

E.g., 'info signal-dispositions 1 2 3 4 5 6 7 8 9 10 11'

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. Yet another thing that can go
away with C++11.

Should probably write a test for this. Will do if people agree this
is useful.

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.
---
gdb/doc/gdb.texinfo | 6 +-
gdb/NEWS | 3 +
gdb/cli/cli-script.c | 200 +++++++++++++++++++++++++---------------------
gdb/common/common-utils.h | 18 +++++
4 files changed, 135 insertions(+), 92 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index b3eb488..4d48469 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
diff --git a/gdb/NEWS b/gdb/NEWS
index 4a61438..2317dd8 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 6302f52..eef5a2f 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 point 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));
+ }
+
+ /* Pop the current user arguments from the stack. */
+ ~scoped_user_args_level ()
+ {
+ delete user_args_stack.back ();
+ user_args_stack.pop_back ();
}
- *user_args;
+};

\f
/* 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_args 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 a9053ff..436daa9 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. */
--
2.5.5