[RFA+doco/NEWS-RFA] Add support for --start option in -exec-run GDB/MI command.

[Joel Brobecker <brobecker at adacore dot com>]

Hello again,

Attached is an updated patch, which includes cleaned-up implementation,
doco + NEWS, and testing.

Again, to summarize, the intent is to provide the GDB/MI equivalent
of the "start" CLI command. The latter searches the executable for
the  name of the main subprogram, and inserts a temporary breakpoint
at that location, before then running the program. This feature is
implemented by adding a "--start" command option to the "-exec-run"
GDB/MI command.

Example of use with an Ada program, where the name of the main
subprogram can be different from "main" (in our example, "simple_main"),
slightly reformatted for easier reading:

> (gdb)
> -exec-run --start
> =breakpoint-created,bkpt={number="1",type="breakpoint",disp="del",
>                           enabled="y",addr="0x0000000000401d70",
>                           func="simple_main",file="simple_main.adb",
>                           fullname="/[...]/simple_main.adb",line="4",
>                           thread-groups=["i1"],times="0",
>                           original-location="_ada_simple_main"}
> =thread-group-started,id="i1",pid="30180"
> =thread-created,id="1",group-id="i1"
> ^running
> *running,thread-id="all"
> (gdb) 
> *stopped,reason="breakpoint-hit",disp="del",bkptno="1",
>          frame={addr="0x0000000000401d70",func="simple_main",args=[],
>                 file="simple_main.adb",fullname="/[...]/simple_main.adb",
>                 line="4"},
>          thread-id="1",stopped-threads="all",core="6"
> =breakpoint-deleted,id="1"

The important elements are the "=breakpoint-created" notification,
as well as the "*stopped" output.

gdb/ChangeLog:

        * mi/mi-main.c (run_one_inferior): Add function description.
        Make ARG a pointer to an integer whose value determines whether
        we should "run" or "start" the program.
        (mi_cmd_exec_run): Add handling of the "--start" option.
        Reject all other command-line options.
        * NEWS: Add entry for "-exec-run"'s new "--start" option.

gdb/doc/ChangeLog:

        * gdb.texinfo (GDB/MI Program Execution): Document "-exec-run"'s
        new "--start" option.

gdb/testsuite/ChangeLog:

        * gdb.mi/mi-start.c, gdb.mi/mi-start.exp: New files.

Tested on x86_64-linux, no regression.
The new testcase was also tested with native-gdbserver.exp, to verify
that it returns untested.

OK to apply?

Thanks,
-- 
Joel

>From 3f8d9cf5b9d05cd51936d14cc2f6de42fb2b36cc Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Tue, 1 Oct 2013 09:55:58 +0200
Subject: [PATCH] Add support for --start option in -exec-run GDB/MI command.

gdb/ChangeLog:

        * mi/mi-main.c (run_one_inferior): Add function description.
        Make ARG a pointer to an integer whose value determines whether
        we should "run" or "start" the program.
        (mi_cmd_exec_run): Add handling of the "--start" option.
        Reject all other command-line options.
        * NEWS: Add entry for "-exec-run"'s new "--start" option.

gdb/doc/ChangeLog:

        * gdb.texinfo (GDB/MI Program Execution): Document "-exec-run"'s
        new "--start" option.

gdb/testsuite/ChangeLog:

        * gdb.mi/mi-start.c, gdb.mi/mi-start.exp: New files.
---
 gdb/NEWS                          |  5 ++++
 gdb/doc/gdb.texinfo               | 10 ++++++--
 gdb/mi/mi-main.c                  | 54 ++++++++++++++++++++++++++++++++++++---
 gdb/testsuite/gdb.mi/mi-start.c   | 22 ++++++++++++++++
 gdb/testsuite/gdb.mi/mi-start.exp | 47 ++++++++++++++++++++++++++++++++++
 5 files changed, 133 insertions(+), 5 deletions(-)
 create mode 100644 gdb/testsuite/gdb.mi/mi-start.c
 create mode 100644 gdb/testsuite/gdb.mi/mi-start.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index b44eb25..c60732d 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -123,6 +123,11 @@ show range-stepping
      -stack-list-variables now accept an option "--skip-unavailable".
      When used, only the available locals or arguments are displayed.
 
+  ** The -exec-run command now accepts an optional "--start" option.
+     When used, the command follows the same semantics as the "start"
+     command, stopping the program's execution at the start of its
+     main subprogram.
+
 * New system-wide configuration scripts
   A GDB installation now provides scripts suitable for use as system-wide
   configuration scripts for the following systems:
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 07d5068..ca68e30 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -31034,7 +31034,7 @@ fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
 @subsubheading Synopsis
 
 @smallexample
- -exec-run [--all | --thread-group N]
+ -exec-run [ --all | --thread-group N ] [ --start ]
 @end smallexample
 
 Starts execution of the inferior from the beginning.  The inferior
@@ -31042,11 +31042,17 @@ executes until either a breakpoint is encountered or the program
 exits.  In the latter case the output will include an exit code, if
 the program has exited exceptionally.
 
-When no option is specified, the current inferior is started.  If the
+When neither the @samp{--all} nor the @samp{--thread-group} option
+is specified, the current inferior is started.  If the
 @samp{--thread-group} option is specified, it should refer to a thread
 group of type @samp{process}, and that thread group will be started.
 If the @samp{--all} option is specified, then all inferiors will be started.
 
+Using the @samp{--start} option instructs the debugger to stop
+the execution at the start of the inferior's main subprogram,
+following the same behavior as the @code{start} command
+(@pxref{Starting}).
+
 @subsubheading @value{GDBN} Command
 
 The corresponding @value{GDBN} command is @samp{run}.
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index a840579..0867e2f 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -364,9 +364,19 @@ mi_cmd_exec_interrupt (char *command, char **argv, int argc)
     }
 }
 
+/* Callback for iterate_over_inferiors which starts the execution
+   of the given inferior.
+
+   ARG is a pointer to an integer whose value, if non-zero, indicates
+   that the program should be stopped when reaching the main subprogram
+   (similar to what the CLI "start" command does).  */
+
 static int
 run_one_inferior (struct inferior *inf, void *arg)
 {
+  int start_p = *(int *) arg;
+  const char *run_cmd = start_p ? "start" : "run";
+
   if (inf->pid != 0)
     {
       if (inf->pid != ptid_get_pid (inferior_ptid))
@@ -386,7 +396,7 @@ run_one_inferior (struct inferior *inf, void *arg)
       switch_to_thread (null_ptid);
       set_current_program_space (inf->pspace);
     }
-  mi_execute_cli_command ("run", target_can_async_p (),
+  mi_execute_cli_command (run_cmd, target_can_async_p (),
 			  target_can_async_p () ? "&" : NULL);
   return 0;
 }
@@ -394,16 +404,54 @@ run_one_inferior (struct inferior *inf, void *arg)
 void
 mi_cmd_exec_run (char *command, char **argv, int argc)
 {
+  int i;
+  int start_p = 0;
+
+  /* Parse the command options.  */
+  enum opt
+    {
+      START_OPT,
+    };
+  static const struct mi_opt opts[] =
+    {
+	{"-start", START_OPT, 0},
+	{NULL, 0, 0},
+    };
+
+  int oind = 0;
+  char *oarg;
+
+  while (1)
+    {
+      int opt = mi_getopt ("-exec-run", argc, argv, opts, &oind, &oarg);
+
+      if (opt < 0)
+	break;
+      switch ((enum opt) opt)
+	{
+	case START_OPT:
+	  start_p = 1;
+	  break;
+	}
+    }
+
+  /* This command does not accept any argument.  Make sure the user
+     did not provide any.  */
+  if (oind != argc)
+    error (_("Invalid argument: %s"), argv[oind]);
+
   if (current_context->all)
     {
       struct cleanup *back_to = save_current_space_and_thread ();
 
-      iterate_over_inferiors (run_one_inferior, NULL);
+      iterate_over_inferiors (run_one_inferior, &start_p);
       do_cleanups (back_to);
     }
   else
     {
-      mi_execute_cli_command ("run", target_can_async_p (),
+      const char *run_cmd = start_p ? "start" : "run";
+
+      mi_execute_cli_command (run_cmd, target_can_async_p (),
 			      target_can_async_p () ? "&" : NULL);
     }
 }
diff --git a/gdb/testsuite/gdb.mi/mi-start.c b/gdb/testsuite/gdb.mi/mi-start.c
new file mode 100644
index 0000000..13d1ac2
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-start.c
@@ -0,0 +1,22 @@
+/* Copyright 2013 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/>.  */
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.mi/mi-start.exp b/gdb/testsuite/gdb.mi/mi-start.exp
new file mode 100644
index 0000000..98dfef4
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-start.exp
@@ -0,0 +1,47 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# 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/>.
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+# The purpose of this testcase is to test the --start option of
+# the -exec-run command. If we cannot use the -exec-run command,
+# then there is no point in running this testcase...
+if [target_info exists use_gdb_stub] {
+     untested "cannot use -exec-run command"
+     return -1
+}
+
+gdb_exit
+if [mi_gdb_start] {
+    continue
+}
+
+standard_testfile mi-start.c
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+     untested "could not build mi-start"
+     return -1
+}
+
+mi_delete_breakpoints
+mi_gdb_reinitialize_dir $srcdir/$subdir
+mi_gdb_reinitialize_dir $srcdir/$subdir
+mi_gdb_load ${binfile}
+
+mi_run_cmd "--start"
+mi_expect_stop "breakpoint-hit" "main" "" ".*mi-start.c" "$decimal" \
+{ "" "disp=\"del\"" } "run to main"
+
-- 
1.8.1.2