Re: [PATCH] Make STARTUP_WITH_SHELL a runtime toggle -- add new "set/show startup-with-shell" option.

Pedro Alves
2013-10-23T14:49:24Z

On 10/23/2013 02:41 PM, Andreas Schwab wrote:
> Pedro Alves <palves@redhat.com> writes:
>
>> +which indicates the shell or the wrapper specified with
>> +@samp{exec-wrapper} crashed, not your program. Most often, this is
>> +caused by something odd in your shell's initialization file---such as
>> +@file{.cshrc} for C-shell, or @file{.bashrc} for BASH. To help
>
> FWIW, when started non-interactively, bash does not read .bashrc.

Eh, yeah, thanks for noticing. I copied that from further below without
thinking about that:

@emph{Warning:} On Unix systems, @value{GDBN} runs your program using
the shell indicated
by your @code{SHELL} environment variable if it exists (or
@code{/bin/sh} if not). If your @code{SHELL} variable names a shell
that runs an initialization file---such as @file{.cshrc} for C-shell, or
@file{.bashrc} for BASH---any variables you set in that file affect
your program. You may wish to move setting of environment variables to
files that are only run when you sign on, such as @file{.login} or
@file{.profile}.

So that's wrong too. I'll fix it as a follow up if the change below
is OK.

(Now that I think about it, I think whenever people report
issues like these, they're not using bash.)

I've added this change on top:

diff --git i/gdb/doc/gdb.texinfo w/gdb/doc/gdb.texinfo
index cf4a7c4..d7a1318 100644
--- i/gdb/doc/gdb.texinfo
+++ w/gdb/doc/gdb.texinfo
@@ -2138,9 +2138,10 @@ to help diagnose program startup failures such as:
which indicates the shell or the wrapper specified with
@samp{exec-wrapper} crashed, not your program. Most often, this is
caused by something odd in your shell's initialization file---such as
-@file{.cshrc} for C-shell, or @file{.bashrc} for BASH. To help
-diagnose such issues, you can disable use of a shell with @kbd{set
-startup-with-shell off}.
+@file{.cshrc} for C-shell, $@file{.zshenv} for the Z shell, or the
+file specified in the @samp{BASH_ENV} environment variable for BASH.
+To help diagnose such issues, you can disable use of a shell with
+@kbd{set startup-with-shell off}.

Below's the full updated patch.

---
Subject: [PATCH] Make STARTUP_WITH_SHELL a runtime toggle -- add new
"set/show startup-with-shell" option.

Occasionaly we hear about people having problems with GDB not being
able to start programs (with "run"/"start"). GDB spawns a shell to
start the program, and most often, it'll be the case that the problem
is actually with the user's shell setup.

GDB has code to disable the use of the shell to start programs.
That's the STARTUP_WITH_SHELL macro that native targets could set to 0
in their nm.h file (though no target actually uses it nowadays).

This patch makes that setting a run-time knob instead. This will be
useful to quickly diagnose such shell issues, and might also come in
handy at other times (such as when debugging the shell itself, if you
don't have a different shell handy).

gdb/
2013-10-23 Pedro Alves <palves@redhat.com>

* NEWS (New options): Mention set/show startup-with-shell.
* config/alpha/nm-osf3.h (START_INFERIOR_TRAPS_EXPECTED): Set to 2
instead of 3.
* fork-child.c (fork_inferior, startup_inferior): Handle 'set
startup-with-shell'.
(show_startup_with_shell): New function.
(_initialize_fork_child): Register the set/show startup-with-shell
commands.
* inf-ptrace.c (inf_ptrace_create_inferior): Remove comment.
* inf-ttrace.c (inf_ttrace_him): Remove comment.
* procfs.c (procfs_init_inferior): Remove comment.
* infcmd.c (startup_with_shell): New global.
* inferior.h (startup_with_shell): Declare global.
(STARTUP_WITH_SHELL): Delete.
(START_INFERIOR_TRAPS_EXPECTED): Set to 1 by default instead of 2.

gdb/doc/
2013-10-23 Pedro Alves <palves@redhat.com>

* gdb.texinfo (Starting): Document set/show startup-with-shell.
---
gdb/NEWS | 5 +++++
gdb/config/alpha/nm-osf3.h | 9 +++++----
gdb/doc/gdb.texinfo | 32 ++++++++++++++++++++++++++++++--
gdb/fork-child.c | 31 +++++++++++++++++++++++++++----
gdb/inf-ptrace.c | 3 ---
gdb/inf-ttrace.c | 3 ---
gdb/infcmd.c | 6 +++++-
gdb/inferior.h | 42 ++++++++++++++++++++++++------------------
gdb/procfs.c | 2 --
9 files changed, 96 insertions(+), 37 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 10834df..6eb5090 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -98,6 +98,11 @@ set range-stepping
show range-stepping
Control whether target-assisted range stepping is enabled.

+set startup-with-shell
+show startup-with-shell
+ Specifies whether Unix child processes are started via a shell or
+ directly.
+
* You can now use a literal value 'unlimited' for options that
interpret 0 or -1 as meaning "unlimited". E.g., "set
trace-buffer-size unlimited" is now an alias for "set
diff --git a/gdb/config/alpha/nm-osf3.h b/gdb/config/alpha/nm-osf3.h
index b3a082d..7dd278a 100644
--- a/gdb/config/alpha/nm-osf3.h
+++ b/gdb/config/alpha/nm-osf3.h
@@ -16,10 +16,11 @@
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */

-/* Number of traps that happen between exec'ing the shell
- to run an inferior, and when we finally get to
- the inferior code. This is 2 on most implementations. */
-#define START_INFERIOR_TRAPS_EXPECTED 3
+/* Number of traps that happen between exec'ing the shell to run an
+ inferior, and when we finally get to the inferior code, not
+ counting the exec for the shell. This is 1 on most
+ implementations. */
+#define START_INFERIOR_TRAPS_EXPECTED 2

/* Don't trace faults under OSF/1, rely on the posting of the appropriate
signal if fault tracing is disabled.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 44fb174..e3dc706 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -2011,8 +2011,10 @@ is used to pass the arguments, so that you may use normal conventions
(such as wildcard expansion or variable substitution) in describing
the arguments.
In Unix systems, you can control which shell is used with the
-@code{SHELL} environment variable.
-@xref{Arguments, ,Your Program's Arguments}.
+@code{SHELL} environment variable. If you do not define @code{SHELL},
+@value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
+use of any shell with the @code{set startup-with-shell} command (see
+below for details).

@item The @emph{environment.}
Your program normally inherits its environment from @value{GDBN}, but you can
@@ -2115,6 +2117,32 @@ environment:
This command is available when debugging locally on most targets, excluding
@sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.

+@kindex set startup-with-shell
+@item set startup-with-shell
+@itemx set startup-with-shell on
+@itemx set startup-with-shell off
+@itemx show set startup-with-shell
+On Unix systems, by default, if a shell is available on your target,
+it is used to pass the arguments of the @code{run} commands to your
+program, so that you may use normal conventions (such as wildcard
+expansion or variable substitution) in describing the arguments.
+However, in some circunstances, it may be useful to disable such use
+of a shell. For example, if you're debugging the shell itself. Or,
+to help diagnose program startup failures such as:
+
+@smallexample
+(@value{GDBP}) During startup program terminated with signal SIGSEGV, Segmentation fault.
+@end smallexample
+
+@noindent
+which indicates the shell or the wrapper specified with
+@samp{exec-wrapper} crashed, not your program. Most often, this is
+caused by something odd in your shell's initialization file---such as
+@file{.cshrc} for C-shell, $@file{.zshenv} for the Z shell, or the
+file specified in the @samp{BASH_ENV} environment variable for BASH.
+To help diagnose such issues, you can disable use of a shell with
+@kbd{set startup-with-shell off}.
+
@kindex set disable-randomization
@item set disable-randomization
@itemx set disable-randomization on
diff --git a/gdb/fork-child.c b/gdb/fork-child.c
index 6820872..ea78ce0 100644
--- a/gdb/fork-child.c
+++ b/gdb/fork-child.c
@@ -150,11 +150,11 @@ fork_inferior (char *exec_file_arg, char *allargs, char **env,
if (exec_file == 0)
exec_file = get_exec_file (1);

- /* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just
- do a fork/exec, no shell, so don't bother figuring out what
- shell. */
+ /* 'startup_with_shell' is declared in inferior.h, and bound to the
+ "set startup-with-shell" option. If 0, we'll just do a
+ fork/exec, no shell, so don't bother figuring out what shell. */
shell_file = shell_file_arg;
- if (STARTUP_WITH_SHELL)
+ if (startup_with_shell)
{
/* Figure out what shell to start up the user program under. */
if (shell_file == NULL)
@@ -419,6 +419,12 @@ startup_inferior (int ntraps)
int terminal_initted = 0;
ptid_t resume_ptid;

+ if (startup_with_shell)
+ {
+ /* One trap extra for exec'ing the shell. */
+ pending_execs++;
+ }
+
if (target_supports_multi_process ())
resume_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
else
@@ -533,6 +539,15 @@ unset_exec_wrapper_command (char *args, int from_tty)
exec_wrapper = NULL;
}

+static void
+show_startup_with_shell (struct ui_file *file, int from_tty,
+ struct cmd_list_element *c, const char *value)
+{
+ fprintf_filtered (file,
+ _("Use of shell to start subprocesses is %s.\n"),
+ value);
+}
+
/* Provide a prototype to silence -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_fork_child;

@@ -550,4 +565,12 @@ Show the wrapper for running programs."), NULL,
add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
_("Disable use of an execution wrapper."),
&unsetlist);
+
+ add_setshow_boolean_cmd ("startup-with-shell", class_support,
+ &startup_with_shell, _("\
+Set use of shell to start subprocesses. The default is on."), _("\
+Show use of shell to start subprocesses."), NULL,
+ NULL,
+ show_startup_with_shell,
+ &setlist, &showlist);
}
diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c
index 9e6e980..bdebe65 100644
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -137,9 +137,6 @@ inf_ptrace_create_inferior (struct target_ops *ops,

discard_cleanups (back_to);

- /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will
- be 1 or 2 depending on whether we're starting without or with a
- shell. */
startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

/* On some targets, there must be some explicit actions taken after
diff --git a/gdb/inf-ttrace.c b/gdb/inf-ttrace.c
index 3ba830f..36bf4cb 100644
--- a/gdb/inf-ttrace.c
+++ b/gdb/inf-ttrace.c
@@ -642,9 +642,6 @@ inf_ttrace_him (struct target_ops *ops, int pid)

push_target (ops);

- /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will
- be 1 or 2 depending on whether we're starting without or with a
- shell. */
startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

/* On some targets, there must be some explicit actions taken after
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 20f8857..4ad8ad3 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -147,6 +147,10 @@ enum stop_stack_kind stop_stack_dummy;

int stopped_by_random_signal;

+/* See inferior.h. */
+
+int startup_with_shell = 1;
+
\f
/* Accessor routines. */

@@ -255,7 +259,7 @@ construct_inferior_arguments (int argc, char **argv)
{
char *result;

- if (STARTUP_WITH_SHELL)
+ if (startup_with_shell)
{
#ifdef __MINGW32__
/* This holds all the characters considered special to the
diff --git a/gdb/inferior.h b/gdb/inferior.h
index fff072b..cf26844 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -257,6 +257,25 @@ extern void notice_new_inferior (ptid_t, int, int);
extern struct value *get_return_value (struct value *function,
struct type *value_type);

+/* Whether to start up the debuggee under a shell.
+
+ If startup-with-shell is set, GDB's "run" will attempt to start up
+ the debuggee under a shell.
+
+ This is in order for argument-expansion to occur. E.g.,
+
+ (gdb) run *
+
+ The "*" gets expanded by the shell into a list of files.
+
+ While this is a nice feature, it may be handy to bypass the shell
+ in some cases. To disable this feature, do "set startup-with-shell
+ false".
+
+ The catch-exec traps expected during start-up will be one more if
+ the target is started up with a shell. */
+extern int startup_with_shell;
+
/* Address at which inferior stopped. */

extern CORE_ADDR stop_pc;
@@ -346,25 +365,12 @@ struct displaced_step_closure *get_displaced_step_closure_by_addr (CORE_ADDR add
#define ON_STACK 1
#define AT_ENTRY_POINT 4

-/* If STARTUP_WITH_SHELL is set, GDB's "run"
- will attempts to start up the debugee under a shell.
- This is in order for argument-expansion to occur. E.g.,
- (gdb) run *
- The "*" gets expanded by the shell into a list of files.
- While this is a nice feature, it turns out to interact badly
- with some of the catch-fork/catch-exec features we have added.
- In particular, if the shell does any fork/exec's before
- the exec of the target program, that can confuse GDB.
- To disable this feature, set STARTUP_WITH_SHELL to 0.
- To enable this feature, set STARTUP_WITH_SHELL to 1.
- The catch-exec traps expected during start-up will
- be 1 if target is not started up with a shell, 2 if it is.
- - RT
- If you disable this, you need to decrement
- START_INFERIOR_TRAPS_EXPECTED in tm.h. */
-#define STARTUP_WITH_SHELL 1
+/* Number of traps that happen between exec'ing the shell to run an
+ inferior, and when we finally get to the inferior code, not
+ counting the exec for the shell. This is 1 on most
+ implementations. Overridden in nm.h files. */
#if !defined(START_INFERIOR_TRAPS_EXPECTED)
-#define START_INFERIOR_TRAPS_EXPECTED 2
+#define START_INFERIOR_TRAPS_EXPECTED 1
#endif

struct private_inferior;
diff --git a/gdb/procfs.c b/gdb/procfs.c
index 5a425ed..e013096 100644
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -4451,8 +4451,6 @@ procfs_init_inferior (struct target_ops *ops, int pid)
thread_change_ptid (pid_to_ptid (pid),
ptid_build (pid, lwpid, 0));

- /* Typically two, one trap to exec the shell, one to exec the
- program being debugged. Defined by "inferior.h". */
startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

#ifdef SYS_syssgi
--
1.7.11.7