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binutils-gdb/gdb/top.h
Simon Marchi e0700ba44c gdb: make string-like set show commands use std::string variable 
String-like settings (var_string, var_filename, var_optional_filename,
var_string_noescape) currently take a pointer to a `char *` storage
variable (typically global) that holds the setting's value.  I'd like to
"mordernize" this by changing them to use an std::string for storage.

An obvious reason is that string operations on std::string are often
easier to write than with C strings.  And they avoid having to do any
manual memory management.

Another interesting reason is that, with `char *`, nullptr and an empty
string often both have the same meaning of "no value".  String settings
are initially nullptr (unless initialized otherwise).  But when doing
"set foo" (where `foo` is a string setting), the setting now points to
an empty string.  For example, solib_search_path is nullptr at startup,
but points to an empty string after doing "set solib-search-path".  This
leads to some code that needs to check for both to check for "no value".
Or some code that converts back and forth between NULL and "" when
getting or setting the value.  I find this very error-prone, because it
is very easy to forget one or the other.  With std::string, we at least
know that the variable is not "NULL".  There is only one way of
representing an empty string setting, that is with an empty string.

I was wondering whether the distinction between NULL and "" would be
important for some setting, but it doesn't seem so.  If that ever
happens, it would be more C++-y and self-descriptive to use
optional<string> anyway.

Actually, there's one spot where this distinction mattered, it's in
init_history, for the test gdb.base/gdbinit-history.exp.  init_history
sets the history filename to the default ".gdb_history" if it sees that
the setting was never set - if history_filename is nullptr.  If
history_filename is an empty string, it means the setting was explicitly
cleared, so it leaves it as-is.  With the change to std::string, this
distinction doesn't exist anymore.  This can be fixed by moving the code
that chooses a good default value for history_filename to
_initialize_top.  This is ran before -ex commands are processed, so an
-ex command can then clear that value if needed (what
gdb.base/gdbinit-history.exp tests).

Another small improvement, in my opinion is that we can now easily
give string parameters initial values, by simply initializing the global
variables, instead of xstrdup-ing it in the _initialize function.

In Python and Guile, when registering a string-like parameter, we
allocate (with new) an std::string that is owned by the param_smob (in
Guile) and the parmpy_object (in Python) objects.

This patch started by changing all relevant add_setshow_* commands to
take an `std::string *` instead of a `char **` and fixing everything
that failed to build.  That includes of course all string setting
variable and their uses.

string_option_def now uses an std::string also, because there's a
connection between options and settings (see
add_setshow_cmds_for_options).

The add_path function in source.c is really complex and twisted, I'd
rather not try to change it to work on an std::string right now.
Instead, I added an overload that copies the std:string to a `char *`
and back.  This means more copying, but this is not used in a hot path
at all, so I think it is acceptable.

Change-Id: I92c50a1bdd8307141cdbacb388248e4e4fc08c93
Co-authored-by: Lancelot SIX <lsix@lancelotsix.com>
2021-10-03 17:53:16 +01:00

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/* Top level stuff for GDB, the GNU debugger.
Copyright (C) 1986-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef TOP_H
#define TOP_H
#include "gdbsupport/buffer.h"
#include "gdbsupport/event-loop.h"
#include "gdbsupport/next-iterator.h"
#include "value.h"
struct tl_interp_info;
/* Prompt state. */
enum prompt_state
{
/* The command line is blocked simulating synchronous execution.
This is used to implement the foreground execution commands
('run', 'continue', etc.). We won't display the prompt and
accept further commands until the execution is actually over. */
PROMPT_BLOCKED,
/* The command finished; display the prompt before returning back to
the top level. */
PROMPT_NEEDED,
/* We've displayed the prompt already, ready for input. */
PROMPTED,
};
/* All about a user interface instance. Each user interface has its
own I/O files/streams, readline state, its own top level
interpreter (for the main UI, this is the interpreter specified
with -i on the command line) and secondary interpreters (for
interpreter-exec ...), etc. There's always one UI associated with
stdin/stdout/stderr, but the user can create secondary UIs, for
example, to create a separate MI channel on its own stdio
streams. */
struct ui
{
/* Create a new UI. */
ui (FILE *instream, FILE *outstream, FILE *errstream);
~ui ();
DISABLE_COPY_AND_ASSIGN (ui);
/* Pointer to next in singly-linked list. */
struct ui *next;
/* Convenient handle (UI number). Unique across all UIs. */
int num;
/* The UI's command line buffer. This is to used to accumulate
input until we have a whole command line. */
struct buffer line_buffer;
/* The callback used by the event loop whenever an event is detected
on the UI's input file descriptor. This function incrementally
builds a buffer where it accumulates the line read up to the
point of invocation. In the special case in which the character
read is newline, the function invokes the INPUT_HANDLER callback
(see below). */
void (*call_readline) (gdb_client_data);
/* The function to invoke when a complete line of input is ready for
processing. */
void (*input_handler) (gdb::unique_xmalloc_ptr<char> &&);
/* True if this UI is using the readline library for command
editing; false if using GDB's own simple readline emulation, with
no editing support. */
int command_editing;
/* Each UI has its own independent set of interpreters. */
struct ui_interp_info *interp_info;
/* True if the UI is in async mode, false if in sync mode. If in
sync mode, a synchronous execution command (e.g, "next") does not
return until the command is finished. If in async mode, then
running a synchronous command returns right after resuming the
target. Waiting for the command's completion is later done on
the top event loop. For the main UI, this starts out disabled,
until all the explicit command line arguments (e.g., `gdb -ex
"start" -ex "next"') are processed. */
int async;
/* The number of nested readline secondary prompts that are
currently active. */
int secondary_prompt_depth;
/* The UI's stdin. Set to stdin for the main UI. */
FILE *stdin_stream;
/* stdio stream that command input is being read from. Set to stdin
normally. Set by source_command to the file we are sourcing.
Set to NULL if we are executing a user-defined command or
interacting via a GUI. */
FILE *instream;
/* Standard output stream. */
FILE *outstream;
/* Standard error stream. */
FILE *errstream;
/* The file descriptor for the input stream, so that we can register
it with the event loop. */
int input_fd;
/* Whether ISATTY returns true on input_fd. Cached here because
quit_force needs to know this _after_ input_fd might be
closed. */
int input_interactive_p;
/* See enum prompt_state's description. */
enum prompt_state prompt_state;
/* The fields below that start with "m_" are "private". They're
meant to be accessed through wrapper macros that make them look
like globals. */
/* The ui_file streams. */
/* Normal results */
struct ui_file *m_gdb_stdout;
/* Input stream */
struct ui_file *m_gdb_stdin;
/* Serious error notifications */
struct ui_file *m_gdb_stderr;
/* Log/debug/trace messages that should bypass normal stdout/stderr
filtering. For moment, always call this stream using
*_unfiltered. In the very near future that restriction shall be
removed - either call shall be unfiltered. (cagney 1999-06-13). */
struct ui_file *m_gdb_stdlog;
/* The current ui_out. */
struct ui_out *m_current_uiout;
};
/* The main UI. This is the UI that is bound to stdin/stdout/stderr.
It always exists and is created automatically when GDB starts
up. */
extern struct ui *main_ui;
/* The current UI. */
extern struct ui *current_ui;
/* The list of all UIs. */
extern struct ui *ui_list;
/* State for SWITCH_THRU_ALL_UIS. */
class switch_thru_all_uis
{
public:
switch_thru_all_uis () : m_iter (ui_list), m_save_ui (&current_ui)
{
current_ui = ui_list;
}
DISABLE_COPY_AND_ASSIGN (switch_thru_all_uis);
/* If done iterating, return true; otherwise return false. */
bool done () const
{
return m_iter == NULL;
}
/* Move to the next UI, setting current_ui if iteration is not yet
complete. */
void next ()
{
m_iter = m_iter->next;
if (m_iter != NULL)
current_ui = m_iter;
}
private:
/* Used to iterate through the UIs. */
struct ui *m_iter;
/* Save and restore current_ui. */
scoped_restore_tmpl<struct ui *> m_save_ui;
};
/* Traverse through all UI, and switch the current UI to the one
being iterated. */
#define SWITCH_THRU_ALL_UIS() \
for (switch_thru_all_uis stau_state; !stau_state.done (); stau_state.next ())
using ui_range = next_range<ui>;
/* An adapter that can be used to traverse over all UIs. */
static inline
ui_range all_uis ()
{
return ui_range (ui_list);
}
/* Register the UI's input file descriptor in the event loop. */
extern void ui_register_input_event_handler (struct ui *ui);
/* Unregister the UI's input file descriptor from the event loop. */
extern void ui_unregister_input_event_handler (struct ui *ui);
/* From top.c. */
extern bool confirm;
extern int inhibit_gdbinit;
/* Print the GDB version banner to STREAM. If INTERACTIVE is false,
then information referring to commands (e.g., "show configuration")
is omitted; this mode is used for the --version command line
option. If INTERACTIVE is true, then interactive commands are
mentioned. */
extern void print_gdb_version (struct ui_file *stream, bool interactive);
extern void print_gdb_configuration (struct ui_file *);
extern void read_command_file (FILE *);
extern void init_history (void);
extern void command_loop (void);
extern int quit_confirm (void);
extern void quit_force (int *, int);
extern void quit_command (const char *, int);
extern void quit_cover (void);
extern void execute_command (const char *, int);
/* If the interpreter is in sync mode (we're running a user command's
list, running command hooks or similars), and we just ran a
synchronous command that started the target, wait for that command
to end. WAS_SYNC indicates whether sync_execution was set before
the command was run. */
extern void maybe_wait_sync_command_done (int was_sync);
/* Wait for a synchronous execution command to end. */
extern void wait_sync_command_done (void);
extern void check_frame_language_change (void);
/* Prepare for execution of a command.
Call this before every command, CLI or MI.
Returns a cleanup to be run after the command is completed. */
extern scoped_value_mark prepare_execute_command (void);
/* This function returns a pointer to the string that is used
by gdb for its command prompt. */
extern const std::string &get_prompt ();
/* This function returns a pointer to the string that is used
by gdb for its command prompt. */
extern void set_prompt (const char *s);
/* Return 1 if UI's current input handler is a secondary prompt, 0
otherwise. */
extern int gdb_in_secondary_prompt_p (struct ui *ui);
/* Perform _initialize initialization. */
extern void gdb_init ();
/* For use by event-top.c. */
/* Variables from top.c. */
extern int source_line_number;
extern std::string source_file_name;
extern bool history_expansion_p;
extern bool server_command;
extern char *lim_at_start;
extern void gdb_add_history (const char *);
extern void show_commands (const char *args, int from_tty);
extern void set_verbose (const char *, int, struct cmd_list_element *);
extern char *handle_line_of_input (struct buffer *cmd_line_buffer,
const char *rl, int repeat,
const char *annotation_suffix);
/* Call at startup to see if the user has requested that gdb start up
quietly. */
extern bool check_quiet_mode ();
#endif
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