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binutils-gdb/gdb/proc-api.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

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/* Machine independent support for Solaris /proc (process file system) for GDB.
Copyright (C) 1999-2021 Free Software Foundation, Inc.
Written by Michael Snyder at Cygnus Solutions.
Based on work by Fred Fish, Stu Grossman, Geoff Noer, and others.
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/>. */
/*
* Pretty-print trace of api calls to the /proc api
*/
#include "defs.h"
#include "gdbcmd.h"
#include "completer.h"
#include <sys/types.h>
#include <sys/procfs.h>
#include <sys/proc.h> /* for struct proc */
#include <sys/user.h> /* for struct user */
#include <fcntl.h> /* for O_RDWR etc. */
#include "gdbsupport/gdb_wait.h"
#include "proc-utils.h"
/* Much of the information used in the /proc interface, particularly for
printing status information, is kept as tables of structures of the
following form. These tables can be used to map numeric values to
their symbolic names and to a string that describes their specific use. */
struct trans {
long value; /* The numeric value */
const char *name; /* The equivalent symbolic value */
const char *desc; /* Short description of value */
};
static bool procfs_trace = false;
static FILE *procfs_file = NULL;
static std::string procfs_filename = "procfs_trace";
static void
prepare_to_trace (void)
{
if (procfs_trace) /* if procfs tracing turned on */
if (procfs_file == NULL) /* if output file not yet open */
procfs_file = fopen (procfs_filename.c_str (), "a"); /* open output file */
}
static void
set_procfs_trace_cmd (const char *args,
int from_tty, struct cmd_list_element *c)
{
#if 0 /* not sure what I might actually need to do here, if anything */
if (procfs_file)
fflush (procfs_file);
#endif
}
static void
set_procfs_file_cmd (const char *args,
int from_tty, struct cmd_list_element *c)
{
/* Just changed the filename for procfs tracing.
If a file was already open, close it. */
if (procfs_file)
fclose (procfs_file);
procfs_file = NULL;
}
static struct trans rw_table[] = {
{ PCAGENT, "PCAGENT", "create agent lwp with regs from argument" },
{ PCCFAULT, "PCCFAULT", "clear current fault" },
{ PCCSIG, "PCCSIG", "clear current signal" },
{ PCDSTOP, "PCDSTOP", "post stop request" },
{ PCKILL, "PCKILL", "post a signal" },
{ PCNICE, "PCNICE", "set nice priority" },
{ PCREAD, "PCREAD", "read from the address space" },
{ PCWRITE, "PCWRITE", "write to the address space" },
{ PCRUN, "PCRUN", "make process/lwp runnable" },
{ PCSASRS, "PCSASRS", "set ancillary state registers" },
{ PCSCRED, "PCSCRED", "set process credentials" },
{ PCSENTRY, "PCSENTRY", "set traced syscall entry set" },
{ PCSET, "PCSET", "set modes" },
{ PCSEXIT, "PCSEXIT", "set traced syscall exit set" },
{ PCSFAULT, "PCSFAULT", "set traced fault set" },
{ PCSFPREG, "PCSFPREG", "set floating point registers" },
{ PCSHOLD, "PCSHOLD", "set signal mask" },
{ PCSREG, "PCSREG", "set general registers" },
{ PCSSIG, "PCSSIG", "set current signal" },
{ PCSTOP, "PCSTOP", "post stop request and wait" },
{ PCSTRACE, "PCSTRACE", "set traced signal set" },
{ PCSVADDR, "PCSVADDR", "set pc virtual address" },
{ PCSXREG, "PCSXREG", "set extra registers" },
{ PCTWSTOP, "PCTWSTOP", "wait for stop, with timeout arg" },
{ PCUNKILL, "PCUNKILL", "delete a pending signal" },
{ PCUNSET, "PCUNSET", "unset modes" },
{ PCWATCH, "PCWATCH", "set/unset watched memory area" },
{ PCWSTOP, "PCWSTOP", "wait for process/lwp to stop, no timeout" },
{ 0, NULL, NULL }
};
static off_t lseek_offset;
int
write_with_trace (int fd, void *varg, size_t len, char *file, int line)
{
int i = ARRAY_SIZE (rw_table) - 1;
int ret;
procfs_ctl_t *arg = (procfs_ctl_t *) varg;
prepare_to_trace ();
if (procfs_trace)
{
procfs_ctl_t opcode = arg[0];
for (i = 0; rw_table[i].name != NULL; i++)
if (rw_table[i].value == opcode)
break;
if (info_verbose)
fprintf (procfs_file ? procfs_file : stdout,
"%s:%d -- ", file, line);
switch (opcode) {
case PCSET:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSET, %s) %s\n",
arg[1] == PR_FORK ? "PR_FORK" :
arg[1] == PR_RLC ? "PR_RLC" :
arg[1] == PR_ASYNC ? "PR_ASYNC" :
"<unknown flag>",
info_verbose ? rw_table[i].desc : "");
break;
case PCUNSET:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCRESET, %s) %s\n",
arg[1] == PR_FORK ? "PR_FORK" :
arg[1] == PR_RLC ? "PR_RLC" :
arg[1] == PR_ASYNC ? "PR_ASYNC" :
"<unknown flag>",
info_verbose ? rw_table[i].desc : "");
break;
case PCSTRACE:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSTRACE) ");
proc_prettyfprint_signalset (procfs_file ? procfs_file : stdout,
(sigset_t *) &arg[1], 0);
break;
case PCSFAULT:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSFAULT) ");
proc_prettyfprint_faultset (procfs_file ? procfs_file : stdout,
(fltset_t *) &arg[1], 0);
break;
case PCSENTRY:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSENTRY) ");
proc_prettyfprint_syscalls (procfs_file ? procfs_file : stdout,
(sysset_t *) &arg[1], 0);
break;
case PCSEXIT:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSEXIT) ");
proc_prettyfprint_syscalls (procfs_file ? procfs_file : stdout,
(sysset_t *) &arg[1], 0);
break;
case PCSHOLD:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSHOLD) ");
proc_prettyfprint_signalset (procfs_file ? procfs_file : stdout,
(sigset_t *) &arg[1], 0);
break;
case PCSSIG:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCSSIG) ");
proc_prettyfprint_signal (procfs_file ? procfs_file : stdout,
arg[1] ? ((siginfo_t *) &arg[1])->si_signo
: 0,
0);
fprintf (procfs_file ? procfs_file : stdout, "\n");
break;
case PCRUN:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCRUN) ");
if (arg[1] & PRCSIG)
fprintf (procfs_file ? procfs_file : stdout, "clearSig ");
if (arg[1] & PRCFAULT)
fprintf (procfs_file ? procfs_file : stdout, "clearFlt ");
if (arg[1] & PRSTEP)
fprintf (procfs_file ? procfs_file : stdout, "step ");
if (arg[1] & PRSABORT)
fprintf (procfs_file ? procfs_file : stdout, "syscallAbort ");
if (arg[1] & PRSTOP)
fprintf (procfs_file ? procfs_file : stdout, "stopReq ");
fprintf (procfs_file ? procfs_file : stdout, "\n");
break;
case PCKILL:
fprintf (procfs_file ? procfs_file : stdout,
"write (PCKILL) ");
proc_prettyfprint_signal (procfs_file ? procfs_file : stdout,
arg[1], 0);
fprintf (procfs_file ? procfs_file : stdout, "\n");
break;
default:
{
if (rw_table[i].name)
fprintf (procfs_file ? procfs_file : stdout,
"write (%s) %s\n",
rw_table[i].name,
info_verbose ? rw_table[i].desc : "");
else
{
if (lseek_offset != -1)
fprintf (procfs_file ? procfs_file : stdout,
"write (<unknown>, %lud bytes at 0x%08lx) \n",
(unsigned long) len, (unsigned long) lseek_offset);
else
fprintf (procfs_file ? procfs_file : stdout,
"write (<unknown>, %lud bytes) \n",
(unsigned long) len);
}
break;
}
}
if (procfs_file)
fflush (procfs_file);
}
errno = 0;
ret = write (fd, (void *) arg, len);
if (procfs_trace && ret != len)
{
fprintf (procfs_file ? procfs_file : stdout,
"[write (%s) FAILED! (%s)]\n",
rw_table[i].name != NULL ?
rw_table[i].name : "<unknown>",
safe_strerror (errno));
if (procfs_file)
fflush (procfs_file);
}
lseek_offset = -1;
return ret;
}
off_t
lseek_with_trace (int fd, off_t offset, int whence, char *file, int line)
{
off_t ret;
prepare_to_trace ();
errno = 0;
ret = lseek (fd, offset, whence);
lseek_offset = ret;
if (procfs_trace && (ret == -1 || errno != 0))
{
fprintf (procfs_file ? procfs_file : stdout,
"[lseek (0x%08lx) FAILED! (%s)]\n",
(unsigned long) offset, safe_strerror (errno));
if (procfs_file)
fflush (procfs_file);
}
return ret;
}
int
open_with_trace (char *filename, int mode, char *file, int line)
{
int ret;
prepare_to_trace ();
errno = 0;
ret = open (filename, mode);
if (procfs_trace)
{
if (info_verbose)
fprintf (procfs_file ? procfs_file : stdout,
"%s:%d -- ", file, line);
if (errno)
{
fprintf (procfs_file ? procfs_file : stdout,
"[open FAILED! (%s) line %d]\\n",
safe_strerror (errno), line);
}
else
{
fprintf (procfs_file ? procfs_file : stdout,
"%d = open (%s, ", ret, filename);
if (mode == O_RDONLY)
fprintf (procfs_file ? procfs_file : stdout, "O_RDONLY) %d\n",
line);
else if (mode == O_WRONLY)
fprintf (procfs_file ? procfs_file : stdout, "O_WRONLY) %d\n",
line);
else if (mode == O_RDWR)
fprintf (procfs_file ? procfs_file : stdout, "O_RDWR) %d\n",
line);
}
if (procfs_file)
fflush (procfs_file);
}
return ret;
}
int
close_with_trace (int fd, char *file, int line)
{
int ret;
prepare_to_trace ();
errno = 0;
ret = close (fd);
if (procfs_trace)
{
if (info_verbose)
fprintf (procfs_file ? procfs_file : stdout,
"%s:%d -- ", file, line);
if (errno)
fprintf (procfs_file ? procfs_file : stdout,
"[close FAILED! (%s)]\n", safe_strerror (errno));
else
fprintf (procfs_file ? procfs_file : stdout,
"%d = close (%d)\n", ret, fd);
if (procfs_file)
fflush (procfs_file);
}
return ret;
}
pid_t
wait_with_trace (int *wstat, char *file, int line)
{
int ret, lstat = 0;
prepare_to_trace ();
if (procfs_trace)
{
if (info_verbose)
fprintf (procfs_file ? procfs_file : stdout,
"%s:%d -- ", file, line);
fprintf (procfs_file ? procfs_file : stdout,
"wait (line %d) ", line);
if (procfs_file)
fflush (procfs_file);
}
errno = 0;
ret = wait (&lstat);
if (procfs_trace)
{
if (errno)
fprintf (procfs_file ? procfs_file : stdout,
"[wait FAILED! (%s)]\n", safe_strerror (errno));
else
fprintf (procfs_file ? procfs_file : stdout,
"returned pid %d, status 0x%x\n", ret, lstat);
if (procfs_file)
fflush (procfs_file);
}
if (wstat)
*wstat = lstat;
return ret;
}
void
procfs_note (const char *msg, const char *file, int line)
{
prepare_to_trace ();
if (procfs_trace)
{
if (info_verbose)
fprintf (procfs_file ? procfs_file : stdout,
"%s:%d -- ", file, line);
fprintf (procfs_file ? procfs_file : stdout, "%s", msg);
if (procfs_file)
fflush (procfs_file);
}
}
void
proc_prettyfprint_status (long flags, int why, int what, int thread)
{
prepare_to_trace ();
if (procfs_trace)
{
if (thread)
fprintf (procfs_file ? procfs_file : stdout,
"Thread %d: ", thread);
proc_prettyfprint_flags (procfs_file ? procfs_file : stdout,
flags, 0);
if (flags & (PR_STOPPED | PR_ISTOP))
proc_prettyfprint_why (procfs_file ? procfs_file : stdout,
why, what, 0);
if (procfs_file)
fflush (procfs_file);
}
}
void _initialize_proc_api ();
void
_initialize_proc_api ()
{
add_setshow_boolean_cmd ("procfs-trace", no_class, &procfs_trace, _("\
Set tracing for /proc api calls."), _("\
Show tracing for /proc api calls."), NULL,
set_procfs_trace_cmd,
NULL, /* FIXME: i18n: */
&setlist, &showlist);
add_setshow_filename_cmd ("procfs-file", no_class, &procfs_filename, _("\
Set filename for /proc tracefile."), _("\
Show filename for /proc tracefile."), NULL,
set_procfs_file_cmd,
NULL, /* FIXME: i18n: */
&setlist, &showlist);
}
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