Add new "$_shell(CMD)" internal function

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.

Approved-By: Andrew Burgess <aburgess@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>
Approved-By: Eli Zaretskii <eliz@gnu.org>
Change-Id: I7e36d451ee6b428cbf41fded415ae2d6b4efaa4e

1 files changed, 92 insertions, 4 deletions

diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 871785d..0c68089 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 (val->type ());
+
+  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 value::allocate_optimized_out (int_type);
+}
+
 void _initialize_cli_cmds ();
 void
 _initialize_cli_cmds ()
@@ -2606,6 +2681,19 @@ 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\
+\n\
+    Usage: $_shell (COMMAND)\n\
+\n\
+    Arguments:\n\
+\n\
+      COMMAND: The command to execute.  Must be a string.\n\
+\n\
+    Returns:\n\
+      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\