From: Pedro Alves <pedro@palves.net>
To: gdb-patches@sourceware.org
Subject: [PATCH 3/6] Add new "$_shell(CMD)" internal function
Date: Fri, 10 Feb 2023 23:36:01 +0000 [thread overview]
Message-ID: <20230210233604.2228450-4-pedro@palves.net> (raw)
In-Reply-To: <20230210233604.2228450-1-pedro@palves.net>
For testing a following patch, I wanted a way to send a SIGINT to GDB
from a breakpoint condition. And I didn't want to do it from a Python
breakpoint or Python function, as I wanted to exercise non-Python code
paths. So I thought I'd add a new $_shell internal function, that
runs a command under the shell, and returns the exit code. With this,
I could write:
(gdb) b foo if $_shell("kill -SIGINT $gdb_pid") != 0 || <other condition>
I think this is generally useful, hence I'm proposing it here.
Here's the new function in action:
(gdb) p $_shell("true")
$1 = 0
(gdb) p $_shell("false")
$2 = 1
(gdb) p $_shell("echo hello")
hello
$3 = 0
(gdb) p $_shell("foobar")
bash: line 1: foobar: command not found
$4 = 127
(gdb) help function _shell
$_shell - execute a shell command and returns the result.
Usage: $_shell (command)
Returns the command's exit code: zero on success, non-zero otherwise.
(gdb)
NEWS and manual changes included.
Change-Id: I7e36d451ee6b428cbf41fded415ae2d6b4efaa4e
---
gdb/NEWS | 10 ++++
gdb/cli/cli-cmds.c | 89 ++++++++++++++++++++++++++++--
gdb/doc/gdb.texinfo | 47 ++++++++++++++++
gdb/testsuite/gdb.base/default.exp | 1 +
gdb/testsuite/gdb.base/shell.exp | 36 ++++++++++++
5 files changed, 179 insertions(+), 4 deletions(-)
diff --git a/gdb/NEWS b/gdb/NEWS
index b85923cf80d..0d3445438b1 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -56,6 +56,16 @@ maintenance info frame-unwinders
List the frame unwinders currently in effect, starting with the highest
priority.
+* New convenience function "$_shell", to execute a shell command and
+ return the result. This lets you run shell commands in expressions.
+ Some examples:
+
+ (gdb) p $_shell("true")
+ $1 = 0
+ (gdb) p $_shell("false")
+ $2 = 1
+ (gdb) break func if $_shell("some command") == 0
+
* MI changes
** mi now reports 'no-history' as a stop reason when hitting the end of the
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 6c0d780face..27fbfb035b3 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -39,6 +39,7 @@
#include "gdbsupport/filestuff.h"
#include "location.h"
#include "block.h"
+#include "valprint.h"
#include "ui-out.h"
#include "interps.h"
@@ -873,6 +874,9 @@ exit_status_set_internal_vars (int exit_status)
clear_internalvar (var_code);
clear_internalvar (var_signal);
+
+ /* Keep the logic here in sync with shell_internal_fn. */
+
if (WIFEXITED (exit_status))
set_internalvar_integer (var_code, WEXITSTATUS (exit_status));
#ifdef __MINGW32__
@@ -893,8 +897,11 @@ exit_status_set_internal_vars (int exit_status)
warning (_("unexpected shell command exit status %d"), exit_status);
}
-static void
-shell_escape (const char *arg, int from_tty)
+/* Run ARG under the shell, and return the exit status. If ARG is
+ NULL, run an interactive shell. */
+
+static int
+run_under_shell (const char *arg, int from_tty)
{
#if defined(CANT_FORK) || \
(!defined(HAVE_WORKING_VFORK) && !defined(HAVE_WORKING_FORK))
@@ -915,7 +922,7 @@ shell_escape (const char *arg, int from_tty)
the shell command we just ran changed it. */
chdir (current_directory);
#endif
- exit_status_set_internal_vars (rc);
+ return rc;
#else /* Can fork. */
int status, pid;
@@ -942,10 +949,21 @@ shell_escape (const char *arg, int from_tty)
waitpid (pid, &status, 0);
else
error (_("Fork failed"));
- exit_status_set_internal_vars (status);
+ return status;
#endif /* Can fork. */
}
+/* Escape out to the shell to run ARG. If ARG is NULL, launch and
+ interactive shell. Sets $_shell_exitcode and $_shell_exitsignal
+ convenience variables based on the exits status. */
+
+static void
+shell_escape (const char *arg, int from_tty)
+{
+ int status = run_under_shell (arg, from_tty);
+ exit_status_set_internal_vars (status);
+}
+
/* Implementation of the "shell" command. */
static void
@@ -2417,6 +2435,63 @@ gdb_maint_setting_str_internal_fn (struct gdbarch *gdbarch,
return str_value_from_setting (*show_cmd->var, gdbarch);
}
+/* Implementation of the convenience function $_shell. */
+
+static struct value *
+shell_internal_fn (struct gdbarch *gdbarch,
+ const struct language_defn *language,
+ void *cookie, int argc, struct value **argv)
+{
+ if (argc != 1)
+ error (_("You must provide one argument for $_shell."));
+
+ value *val = argv[0];
+ struct type *type = check_typedef (value_type (val));
+
+ if (!language->is_string_type_p (type))
+ error (_("Argument must be a string."));
+
+ value_print_options opts;
+ get_no_prettyformat_print_options (&opts);
+
+ string_file stream;
+ value_print (val, &stream, &opts);
+
+ /* We should always have two quote chars, which we'll strip. */
+ gdb_assert (stream.size () >= 2);
+
+ /* Now strip them. We don't need the original string, so it's
+ cheaper to do it in place, avoiding a string allocation. */
+ std::string str = stream.release ();
+ str[str.size () - 1] = 0;
+ const char *command = str.c_str () + 1;
+
+ int exit_status = run_under_shell (command, 0);
+
+ struct type *int_type = builtin_type (gdbarch)->builtin_int;
+
+ /* Keep the logic here in sync with
+ exit_status_set_internal_vars. */
+
+ if (WIFEXITED (exit_status))
+ return value_from_longest (int_type, WEXITSTATUS (exit_status));
+#ifdef __MINGW32__
+ else if (WIFSIGNALED (exit_status) && WTERMSIG (exit_status) == -1)
+ {
+ /* See exit_status_set_internal_vars. */
+ return value_from_longest (int_type, exit_status);
+ }
+#endif
+ else if (WIFSIGNALED (exit_status))
+ {
+ /* (0x80 | SIGNO) is what most (all?) POSIX-like shells set as
+ exit code on fatal signal termination. */
+ return value_from_longest (int_type, 0x80 | WTERMSIG (exit_status));
+ }
+ else
+ return allocate_optimized_out_value (int_type);
+}
+
void _initialize_cli_cmds ();
void
_initialize_cli_cmds ()
@@ -2606,6 +2681,12 @@ Some integer settings accept an unlimited value, returned\n\
as 0 or -1 depending on the setting."),
gdb_maint_setting_internal_fn, NULL);
+ add_internal_function ("_shell", _("\
+$_shell - execute a shell command and return the result.\n\
+Usage: $_shell (command)\n\
+Returns the command's exit code: zero on success, non-zero otherwise."),
+ shell_internal_fn, NULL);
+
add_cmd ("commands", no_set_class, show_commands, _("\
Show the history of commands you typed.\n\
You can supply a command number to start with, or a `+' to start after\n\
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 7b128053b5a..b2552173093 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -1629,6 +1629,10 @@ the default shell (@file{/bin/sh} on GNU and Unix systems,
@file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
@end table
+You may also invoke shell commands from expressions, using the
+@code{$_shell} convenience function. @xref{$_shell convenience
+function}.
+
The utility @code{make} is often needed in development environments.
You do not have to use the @code{shell} command for this purpose in
@value{GDBN}:
@@ -12969,6 +12973,49 @@ Like the @code{$_gdb_setting_str} function, but works with
Like the @code{$_gdb_setting} function, but works with
@code{maintenance set} variables.
+@anchor{$_shell convenience function}
+@item $_shell (@var{command-string})
+@findex $_shell@r{, convenience function}
+
+Invoke a standard shell to execute @var{command-string}. Returns the
+command's exit status. On Unix systems, a command which exits with a
+zero exit status has succeeded, and non-zero exit status indicates
+failure. When a command terminates on a fatal signal whose number is
+N, @value{GDBN} uses the value 128+N as the exit status, as is
+standard in Unix shells. The shell to run is determined in the same
+way as for the @code{shell} command. @xref{Shell Commands, ,Shell
+Commands}. The shell runs on the host machine, the machine
+@value{GDBN} is running on.
+
+@smallexample
+(@value{GDBP}) print $_shell("true")
+$1 = 0
+(@value{GDBP}) print $_shell("false")
+$2 = 1
+(@value{GDBP}) p $_shell("echo hello")
+hello
+$3 = 0
+(@value{GDBP}) p $_shell("foobar")
+bash: line 1: foobar: command not found
+$4 = 127
+@end smallexample
+
+This may also be useful in breakpoint conditions. For example:
+
+@smallexample
+(@value{GDBP}) break function if $_shell("some command") == 0
+@end smallexample
+
+In this scenario, you'll want to make sure that the shell command you
+run in the breakpoint condition takes the least amount of time
+possible. This is important to minimize the time it takes to evaluate
+the condition and re-resume the program if the condition turns out to
+be false.
+
+Note: unlike the @code{shell} command, the @code{$_shell} convenience
+function does not affect the @code{$_shell_exitcode} and
+@code{$_shell_exitsignal} convenience variables.
+
@end table
The following functions require @value{GDBN} to be configured with
diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
index d0789a64401..7e73db0576a 100644
--- a/gdb/testsuite/gdb.base/default.exp
+++ b/gdb/testsuite/gdb.base/default.exp
@@ -606,6 +606,7 @@ set show_conv_list \
{$_cimag = <internal function _cimag>} \
{$_creal = <internal function _creal>} \
{$_isvoid = <internal function _isvoid>} \
+ {$_shell = <internal function _shell>} \
{$_gdb_maint_setting_str = <internal function _gdb_maint_setting_str>} \
{$_gdb_maint_setting = <internal function _gdb_maint_setting>} \
{$_gdb_setting_str = <internal function _gdb_setting_str>} \
diff --git a/gdb/testsuite/gdb.base/shell.exp b/gdb/testsuite/gdb.base/shell.exp
index 31cdcb41af5..ba1691ea2b0 100644
--- a/gdb/testsuite/gdb.base/shell.exp
+++ b/gdb/testsuite/gdb.base/shell.exp
@@ -41,6 +41,42 @@ if { ! [ishost *-*-mingw*] } {
gdb_test "p \$_shell_exitsignal" " = 2" "shell interrupt exitsignal"
}
+# Test the $_shell convenience function.
+
+with_test_prefix "\$_shell convenience function" {
+ # Simple commands, check the result code.
+ gdb_test "p \$_shell(\"true\")" " = 0"
+ gdb_test "p \$_shell(\"false\")" " = 1"
+
+ # Test command with arguments.
+ gdb_test "p \$_shell(\"echo foo\")" "foo\r\n\\$${decimal} = 0"
+
+ # Check the type of the result.
+ gdb_test "ptype \$_shell(\"true\")" "type = int"
+
+ # Test passing a non-literal string as command name.
+ gdb_test "p \$cmd = \"echo bar\"" " = \"echo bar\""
+ gdb_test "p \$_shell(\$cmd)" "bar\r\n\\$${decimal} = 0"
+
+ # Test executing a non-existing command. The result is
+ # shell-dependent, but most (all?) POSIX-like shells return 127 in
+ # this case.
+ gdb_test "p \$_shell(\"non-existing-command-foo-bar-qux\")" " = 127"
+
+ gdb_test "p \$_shell" \
+ " = <internal function _shell>"
+ gdb_test "ptype \$_shell" \
+ "type = <internal function>"
+
+ # Test error scenarios.
+ gdb_test "p \$_shell()" \
+ "You must provide one argument for \\\$_shell\\\."
+ gdb_test "p \$_shell(\"a\", \"b\")" \
+ "You must provide one argument for \\\$_shell\\\."
+ gdb_test "p \$_shell(1)" \
+ "Argument must be a string\\\."
+}
+
# Define the user command "foo", used to test "pipe" command.
gdb_test_multiple "define foo" "define foo" {
-re "End with" {
--
2.36.0
next prev parent reply other threads:[~2023-02-10 23:36 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-10 23:35 [PATCH 0/6] Don't throw quit while handling inferior events Pedro Alves
2023-02-10 23:35 ` [PATCH 1/6] Fix "ptype INTERNAL_FUNC" (PR gdb/30105) Pedro Alves
2023-02-13 16:02 ` Andrew Burgess
2023-02-14 15:26 ` Tom Tromey
2023-02-15 21:10 ` Pedro Alves
2023-02-15 22:04 ` Tom Tromey
2023-02-10 23:36 ` [PATCH 2/6] Make "ptype INTERNAL_FUNCTION" in Ada print like other languages Pedro Alves
2023-02-13 16:02 ` Andrew Burgess
2023-02-14 15:30 ` Tom Tromey
2023-02-15 13:38 ` Pedro Alves
2023-02-15 15:13 ` Pedro Alves
2023-02-15 16:56 ` Tom Tromey
2023-02-15 21:04 ` [PATCH] Move TYPE_CODE_INTERNAL_FUNCTION type printing to common code (was: Re: [PATCH 2/6] Make "ptype INTERNAL_FUNCTION" in Ada print like other languages) Pedro Alves
2023-02-20 15:28 ` Andrew Burgess
2023-02-10 23:36 ` Pedro Alves [this message]
2023-02-11 8:02 ` [PATCH 3/6] Add new "$_shell(CMD)" internal function Eli Zaretskii
2023-02-13 15:11 ` Pedro Alves
2023-02-13 15:36 ` Eli Zaretskii
2023-02-13 16:47 ` [PATCH] gdb/manual: Move @findex entries (was: Re: [PATCH 3/6] Add new "$_shell(CMD)" internal function) Pedro Alves
2023-02-13 17:00 ` Eli Zaretskii
2023-02-13 17:27 ` [PATCH 3/6] Add new "$_shell(CMD)" internal function Pedro Alves
2023-02-13 18:41 ` Eli Zaretskii
2023-02-14 15:38 ` Tom Tromey
2023-02-10 23:36 ` [PATCH 4/6] Don't throw quit while handling inferior events Pedro Alves
2023-02-14 15:50 ` Tom Tromey
2023-02-10 23:36 ` [PATCH 5/6] GC get_active_ext_lang Pedro Alves
2023-02-14 15:39 ` Tom Tromey
2023-02-10 23:36 ` [PATCH 6/6] Don't throw quit while handling inferior events, part II Pedro Alves
2023-02-14 15:54 ` Tom Tromey
2023-02-15 21:16 ` Pedro Alves
2023-02-15 21:24 ` Pedro Alves
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