binutils-gdb/gdb/mi/mi-cmd-env.c
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

282 lines
6.3 KiB
C

/* MI Command Set - environment commands.
Copyright (C) 2002-2021 Free Software Foundation, Inc.
Contributed by Red Hat 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/>. */
#include "defs.h"
#include "inferior.h"
#include "value.h"
#include "mi-out.h"
#include "mi-cmds.h"
#include "mi-getopt.h"
#include "symtab.h"
#include "target.h"
#include "gdbsupport/environ.h"
#include "command.h"
#include "ui-out.h"
#include "top.h"
#include <sys/stat.h>
#include "source.h"
static const char path_var_name[] = "PATH";
static char *orig_path = NULL;
/* The following is copied from mi-main.c so for m1 and below we can
perform old behavior and use cli commands. If ARGS is non-null,
append it to the CMD. */
static void
env_execute_cli_command (const char *cmd, const char *args)
{
if (cmd != 0)
{
gdb::unique_xmalloc_ptr<char> run;
if (args != NULL)
run.reset (xstrprintf ("%s %s", cmd, args));
else
run.reset (xstrdup (cmd));
execute_command ( /*ui */ run.get (), 0 /*from_tty */ );
}
}
/* Print working directory. */
void
mi_cmd_env_pwd (const char *command, char **argv, int argc)
{
struct ui_out *uiout = current_uiout;
if (argc > 0)
error (_("-environment-pwd: No arguments allowed"));
if (mi_version (uiout) < 2)
{
env_execute_cli_command ("pwd", NULL);
return;
}
/* Otherwise the mi level is 2 or higher. */
gdb::unique_xmalloc_ptr<char> cwd (getcwd (NULL, 0));
if (cwd == NULL)
error (_("-environment-pwd: error finding name of working directory: %s"),
safe_strerror (errno));
uiout->field_string ("cwd", cwd.get ());
}
/* Change working directory. */
void
mi_cmd_env_cd (const char *command, char **argv, int argc)
{
if (argc == 0 || argc > 1)
error (_("-environment-cd: Usage DIRECTORY"));
env_execute_cli_command ("cd", argv[0]);
}
static void
env_mod_path (const char *dirname, std::string &which_path)
{
if (dirname == 0 || dirname[0] == '\0')
return;
/* Call add_path with last arg 0 to indicate not to parse for
separator characters. */
add_path (dirname, which_path, 0);
}
/* Add one or more directories to start of executable search path. */
void
mi_cmd_env_path (const char *command, char **argv, int argc)
{
struct ui_out *uiout = current_uiout;
const char *env;
int reset = 0;
int oind = 0;
int i;
char *oarg;
enum opt
{
RESET_OPT
};
static const struct mi_opt opts[] =
{
{"r", RESET_OPT, 0},
{ 0, 0, 0 }
};
dont_repeat ();
if (mi_version (uiout) < 2)
{
for (i = argc - 1; i >= 0; --i)
env_execute_cli_command ("path", argv[i]);
return;
}
/* Otherwise the mi level is 2 or higher. */
while (1)
{
int opt = mi_getopt ("-environment-path", argc, argv, opts,
&oind, &oarg);
if (opt < 0)
break;
switch ((enum opt) opt)
{
case RESET_OPT:
reset = 1;
break;
}
}
argv += oind;
argc -= oind;
std::string exec_path;
if (reset)
{
/* Reset implies resetting to original path first. */
exec_path = orig_path;
}
else
{
/* Otherwise, get current path to modify. */
env = current_inferior ()->environment.get (path_var_name);
/* Can be null if path is not set. */
if (!env)
env = "";
exec_path = env;
}
for (i = argc - 1; i >= 0; --i)
env_mod_path (argv[i], exec_path);
current_inferior ()->environment.set (path_var_name, exec_path.c_str ());
env = current_inferior ()->environment.get (path_var_name);
uiout->field_string ("path", env);
}
/* Add zero or more directories to the front of the source path. */
void
mi_cmd_env_dir (const char *command, char **argv, int argc)
{
struct ui_out *uiout = current_uiout;
int i;
int oind = 0;
int reset = 0;
char *oarg;
enum opt
{
RESET_OPT
};
static const struct mi_opt opts[] =
{
{"r", RESET_OPT, 0},
{ 0, 0, 0 }
};
dont_repeat ();
if (mi_version (uiout) < 2)
{
for (i = argc - 1; i >= 0; --i)
env_execute_cli_command ("dir", argv[i]);
return;
}
/* Otherwise mi level is 2 or higher. */
while (1)
{
int opt = mi_getopt ("-environment-directory", argc, argv, opts,
&oind, &oarg);
if (opt < 0)
break;
switch ((enum opt) opt)
{
case RESET_OPT:
reset = 1;
break;
}
}
argv += oind;
argc -= oind;
if (reset)
{
/* Reset means setting to default path first. */
init_source_path ();
}
for (i = argc - 1; i >= 0; --i)
env_mod_path (argv[i], source_path);
uiout->field_string ("source-path", source_path);
forget_cached_source_info ();
}
/* Set the inferior terminal device name. */
void
mi_cmd_inferior_tty_set (const char *command, char **argv, int argc)
{
if (argc > 0)
current_inferior ()->set_tty (argv[0]);
else
current_inferior ()->set_tty ("");
}
/* Print the inferior terminal device name. */
void
mi_cmd_inferior_tty_show (const char *command, char **argv, int argc)
{
if ( !mi_valid_noargs ("-inferior-tty-show", argc, argv))
error (_("-inferior-tty-show: Usage: No args"));
const std::string &inferior_tty = current_inferior ()->tty ();
if (!inferior_tty.empty ())
current_uiout->field_string ("inferior_tty_terminal", inferior_tty);
}
void _initialize_mi_cmd_env ();
void
_initialize_mi_cmd_env ()
{
const char *env;
/* We want original execution path to reset to, if desired later.
At this point, current inferior is not created, so cannot use
current_inferior ()->environment. We use getenv here because it
is not necessary to create a whole new gdb_environ just for one
variable. */
env = getenv (path_var_name);
/* Can be null if path is not set. */
if (!env)
env = "";
orig_path = xstrdup (env);
}