* target.h (struct regcache): Add forward declaration.

[deliverable/binutils-gdb.git] / gdb / inferior.h

diff --git a/gdb/inferior.h b/gdb/inferior.h
index 26798a50d74d93f685a485f0af62459005b34921..e93e413bb75f8bb5e5875c5fcddbffb611a27cba 100644 (file)
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -1,6 +1,9 @@
 /* Variables that describe the inferior process running under GDB:
    Where it is, why it stopped, and how to step it.
 /* Variables that describe the inferior process running under GDB:
    Where it is, why it stopped, and how to step it.

-   Copyright 1986, 1989, 1992, 1996, 1998 Free Software Foundation, Inc.
+
+   Copyright (C) 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
+   1998, 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007
+   Free Software Foundation, Inc.

 
    This file is part of GDB.
 
 
    This file is part of GDB.
 


@@ -16,18 +19,28 @@
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software

-   Foundation, Inc., 59 Temple Place - Suite 330,
-   Boston, MA 02111-1307, USA.  */
+   Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.  */

 
 #if !defined (INFERIOR_H)
 #define INFERIOR_H 1
 
 
 #if !defined (INFERIOR_H)
 #define INFERIOR_H 1
 

+struct target_waitstatus;
+struct frame_info;
+struct ui_file;
+struct type;
+struct gdbarch;
+struct regcache;
+

 /* For bpstat.  */
 #include "breakpoint.h"
 
 /* For enum target_signal.  */
 #include "target.h"
 
 /* For bpstat.  */
 #include "breakpoint.h"
 
 /* For enum target_signal.  */
 #include "target.h"
 

+/* For struct frame_id.  */
+#include "frame.h"
+

 /* Structure in which to save the status of the inferior.  Create/Save
    through "save_inferior_status", restore through
    "restore_inferior_status".
 /* Structure in which to save the status of the inferior.  Create/Save
    through "save_inferior_status", restore through
    "restore_inferior_status".


@@ -50,13 +63,37 @@ extern void write_inferior_status_register (struct inferior_status
                                            *inf_status, int regno,
                                            LONGEST val);
 
                                            *inf_status, int regno,
                                            LONGEST val);
 

-/* This macro gives the number of registers actually in use by the
-   inferior.  This may be less than the total number of registers,
-   perhaps depending on the actual CPU in use or program being run.  */
+/* The -1 ptid, often used to indicate either an error condition
+   or a "don't care" condition, i.e, "run all threads."  */
+extern ptid_t minus_one_ptid;

 
 

-#ifndef ARCH_NUM_REGS
-#define ARCH_NUM_REGS NUM_REGS
-#endif
+/* The null or zero ptid, often used to indicate no process. */
+extern ptid_t null_ptid;
+
+/* Attempt to find and return an existing ptid with the given PID, LWP,
+   and TID components.  If none exists, create a new one and return
+   that.  */
+ptid_t ptid_build (int pid, long lwp, long tid);
+
+/* Find/Create a ptid from just a pid. */
+ptid_t pid_to_ptid (int pid);
+
+/* Fetch the pid (process id) component from a ptid. */
+int ptid_get_pid (ptid_t ptid);
+
+/* Fetch the lwp (lightweight process) component from a ptid. */
+long ptid_get_lwp (ptid_t ptid);
+
+/* Fetch the tid (thread id) component from a ptid. */
+long ptid_get_tid (ptid_t ptid);
+
+/* Compare two ptids to see if they are equal */
+extern int ptid_equal (ptid_t p1, ptid_t p2);
+
+/* Save value of inferior_ptid so that it may be restored by
+   a later call to do_cleanups().  Returns the struct cleanup
+   pointer needed for later doing the cleanup.  */
+extern struct cleanup * save_inferior_ptid (void);

 
 extern void set_sigint_trap (void);
 
 
 extern void set_sigint_trap (void);
 


@@ -66,13 +103,15 @@ extern void set_sigio_trap (void);
 
 extern void clear_sigio_trap (void);
 
 
 extern void clear_sigio_trap (void);
 

-/* File name for default use for standard in/out in the inferior.  */
+/* Set/get file name for default use for standard in/out in the inferior.  */

 
 

-extern char *inferior_io_terminal;
+extern void set_inferior_io_terminal (const char *terminal_name);
+extern const char *get_inferior_io_terminal (void);

 
 

-/* Pid of our debugged inferior, or 0 if no inferior now.  */
+/* Collected pid, tid, etc. of the debugged inferior.  When there's
+   no inferior, PIDGET (inferior_ptid) will be 0. */

 
 

-extern int inferior_pid;
+extern ptid_t inferior_ptid;

 
 /* Is the inferior running right now, as a result of a 'run&',
    'continue&' etc command? This is used in asycn gdb to determine
 
 /* Is the inferior running right now, as a result of a 'run&',
    'continue&' etc command? This is used in asycn gdb to determine


@@ -85,7 +124,7 @@ extern int target_executing;
    redisplay the prompt until the execution is actually over. */
 extern int sync_execution;
 
    redisplay the prompt until the execution is actually over. */
 extern int sync_execution;
 

-/* This is only valid when inferior_pid is non-zero.
+/* This is only valid when inferior_ptid is non-zero.

 
    If this is 0, then exec events should be noticed and responded to
    by the debugger (i.e., be reported to the user).
 
    If this is 0, then exec events should be noticed and responded to
    by the debugger (i.e., be reported to the user).


@@ -108,64 +147,44 @@ extern int inferior_ignoring_leading_exec_events;
 
 /* Inferior environment. */
 
 
 /* Inferior environment. */
 

-extern struct environ *inferior_environ;
-
-/* Character array containing an image of the inferior programs'
-   registers. */
-
-extern char *registers;
-
-/* Character array containing the current state of each register
-   (unavailable<0, valid=0, invalid>0). */
-
-extern signed char *register_valid;
+extern struct gdb_environ *inferior_environ;

 
 extern void clear_proceed_status (void);
 
 extern void proceed (CORE_ADDR, enum target_signal, int);
 
 
 extern void clear_proceed_status (void);
 
 extern void proceed (CORE_ADDR, enum target_signal, int);
 

+/* When set, stop the 'step' command if we enter a function which has
+   no line number information.  The normal behavior is that we step
+   over such function.  */
+extern int step_stop_if_no_debug;
+

 extern void kill_inferior (void);
 
 extern void generic_mourn_inferior (void);
 
 extern void kill_inferior (void);
 
 extern void generic_mourn_inferior (void);
 

-extern void terminal_ours (void);
+extern void terminal_save_ours (void);

 
 

-extern int run_stack_dummy (CORE_ADDR, char *);
+extern void terminal_ours (void);

 
 extern CORE_ADDR read_pc (void);
 
 
 extern CORE_ADDR read_pc (void);
 

-extern CORE_ADDR read_pc_pid (int);
-
-extern CORE_ADDR generic_target_read_pc (int);
+extern CORE_ADDR read_pc_pid (ptid_t);

 
 extern void write_pc (CORE_ADDR);
 
 
 extern void write_pc (CORE_ADDR);
 

-extern void write_pc_pid (CORE_ADDR, int);
+extern void write_pc_pid (CORE_ADDR, ptid_t);

 
 

-extern void generic_target_write_pc (CORE_ADDR, int);
+extern void generic_target_write_pc (CORE_ADDR, ptid_t);

 
 extern CORE_ADDR read_sp (void);
 
 
 extern CORE_ADDR read_sp (void);
 

-extern CORE_ADDR generic_target_read_sp (void);
-
-extern void write_sp (CORE_ADDR);
-
-extern void generic_target_write_sp (CORE_ADDR);
-
-extern CORE_ADDR read_fp (void);
-
-extern CORE_ADDR generic_target_read_fp (void);
-
-extern void write_fp (CORE_ADDR);
-
-extern void generic_target_write_fp (CORE_ADDR);
-
-extern CORE_ADDR unsigned_pointer_to_address (struct type *type, void *buf);
-
-extern void unsigned_address_to_pointer (struct type *type, void *buf,
+extern CORE_ADDR unsigned_pointer_to_address (struct type *type,
+                                             const gdb_byte *buf);
+extern void unsigned_address_to_pointer (struct type *type, gdb_byte *buf,

                                         CORE_ADDR addr);
                                         CORE_ADDR addr);

-extern CORE_ADDR signed_pointer_to_address (struct type *type, void *buf);
-extern void address_to_signed_pointer (struct type *type, void *buf,
+extern CORE_ADDR signed_pointer_to_address (struct type *type,
+                                           const gdb_byte *buf);
+extern void address_to_signed_pointer (struct type *type, gdb_byte *buf,

                                       CORE_ADDR addr);
 
 extern void wait_for_inferior (void);
                                       CORE_ADDR addr);
 
 extern void wait_for_inferior (void);


@@ -185,11 +204,14 @@ extern void resume (int, enum target_signal);
 
 /* From misc files */
 
 
 /* From misc files */
 

-extern void store_inferior_registers (int);
+extern void default_print_registers_info (struct gdbarch *gdbarch,
+                                         struct ui_file *file,
+                                         struct frame_info *frame,
+                                         int regnum, int all);

 
 

-extern void fetch_inferior_registers (int);
+extern void store_inferior_registers (struct regcache *, int);

 
 

-extern void solib_create_inferior_hook (void);
+extern void fetch_inferior_registers (struct regcache *, int);

 
 extern void child_terminal_info (char *, int);
 
 
 extern void child_terminal_info (char *, int);
 


@@ -207,26 +229,14 @@ extern void terminal_init_inferior_with_pgrp (int pgrp);
 
 extern int attach (int);
 
 
 extern int attach (int);
 

-#if !defined(REQUIRE_ATTACH)
-#define REQUIRE_ATTACH attach
-#endif
-
-#if !defined(REQUIRE_DETACH)
-#define REQUIRE_DETACH(pid,siggnal) detach (siggnal)
-#endif
-

 extern void detach (int);
 
 /* PTRACE method of waiting for inferior process.  */
 extern void detach (int);
 
 /* PTRACE method of waiting for inferior process.  */

-int ptrace_wait (int, int *);
-
-extern void child_resume (int, int, enum target_signal);
+int ptrace_wait (ptid_t, int *);

 
 

-#ifndef PTRACE_ARG3_TYPE
-#define PTRACE_ARG3_TYPE int   /* Correct definition for most systems. */
-#endif
+extern void child_resume (ptid_t, int, enum target_signal);

 
 

-extern int call_ptrace (int, int, PTRACE_ARG3_TYPE, int);
+extern int call_ptrace (int, int, PTRACE_TYPE_ARG3, int);

 
 extern void pre_fork_inferior (void);
 
 
 extern void pre_fork_inferior (void);
 


@@ -234,7 +244,7 @@ extern void pre_fork_inferior (void);
 
 extern int proc_iterate_over_mappings (int (*)(int, CORE_ADDR));
 
 
 extern int proc_iterate_over_mappings (int (*)(int, CORE_ADDR));
 

-extern int procfs_first_available (void);
+extern ptid_t procfs_first_available (void);

 
 /* From fork-child.c */
 
 
 /* From fork-child.c */
 


@@ -243,19 +253,19 @@ extern void fork_inferior (char *, char *, char **,
                           void (*)(int), void (*)(void), char *);
 
 
                           void (*)(int), void (*)(void), char *);
 
 

-extern void clone_and_follow_inferior (int, int *);
-

 extern void startup_inferior (int);
 
 extern void startup_inferior (int);
 

+extern char *construct_inferior_arguments (struct gdbarch *, int, char **);
+

 /* From inflow.c */
 
 /* From inflow.c */
 

-extern void new_tty_prefork (char *);
+extern void new_tty_prefork (const char *);

 
 extern int gdb_has_a_terminal (void);
 
 /* From infrun.c */
 
 
 extern int gdb_has_a_terminal (void);
 
 /* From infrun.c */
 

-extern void start_remote (void);
+extern void start_remote (int from_tty);

 
 extern void normal_stop (void);
 
 
 extern void normal_stop (void);
 


@@ -271,12 +281,35 @@ extern int signal_print_update (int, int);
 
 extern int signal_pass_update (int, int);
 
 
 extern int signal_pass_update (int, int);
 

+extern void get_last_target_status(ptid_t *ptid,
+                                   struct target_waitstatus *status);
+
+extern void follow_inferior_reset_breakpoints (void);
+

 /* From infcmd.c */
 
 extern void tty_command (char *, int);
 
 /* From infcmd.c */
 
 extern void tty_command (char *, int);
 

+extern void post_create_inferior (struct target_ops *, int);
+

 extern void attach_command (char *, int);
 
 extern void attach_command (char *, int);
 

+extern char *get_inferior_args (void);
+
+extern char *set_inferior_args (char *);
+
+extern void set_inferior_args_vector (int, char **);
+
+extern void registers_info (char *, int);
+
+extern void nexti_command (char *, int);
+
+extern void stepi_command (char *, int);
+
+extern void continue_command (char *, int);
+
+extern void interrupt_target_command (char *args, int from_tty);
+

 /* Last signal that the inferior received (why it stopped).  */
 
 extern enum target_signal stop_signal;
 /* Last signal that the inferior received (why it stopped).  */
 
 extern enum target_signal stop_signal;


@@ -323,16 +356,19 @@ extern CORE_ADDR step_range_end;  /* Exclusive */
    This is how we know when we step into a subroutine call,
    and how to set the frame for the breakpoint used to step out.  */
 
    This is how we know when we step into a subroutine call,
    and how to set the frame for the breakpoint used to step out.  */
 

-extern CORE_ADDR step_frame_address;
-
-/* Our notion of the current stack pointer.  */
-
-extern CORE_ADDR step_sp;
+extern struct frame_id step_frame_id;

 
 /* 1 means step over all subroutine calls.
    -1 means step over calls to undebuggable functions.  */
 
 
 /* 1 means step over all subroutine calls.
    -1 means step over calls to undebuggable functions.  */
 

-extern int step_over_calls;
+enum step_over_calls_kind
+  {
+    STEP_OVER_NONE,
+    STEP_OVER_ALL,
+    STEP_OVER_UNDEBUGGABLE
+  };
+
+extern enum step_over_calls_kind step_over_calls;

 
 /* If stepping, nonzero means step count is > 1
    so don't print frame next time inferior stops
 
 /* If stepping, nonzero means step count is > 1
    so don't print frame next time inferior stops


@@ -340,12 +376,37 @@ extern int step_over_calls;
 
 extern int step_multi;
 
 
 extern int step_multi;
 

-/* Nonzero means expecting a trap and caller will handle it themselves.
-   It is used after attach, due to attaching to a process;
-   when running in the shell before the child program has been exec'd;
-   and when running some kinds of remote stuff (FIXME?).  */
-
-extern int stop_soon_quietly;
+/* Nonzero means expecting a trap and caller will handle it
+   themselves.  It is used when running in the shell before the child
+   program has been exec'd; and when running some kinds of remote
+   stuff (FIXME?).  */
+
+/* It is also used after attach, due to attaching to a process. This
+   is a bit trickier.  When doing an attach, the kernel stops the
+   debuggee with a SIGSTOP.  On newer GNU/Linux kernels (>= 2.5.61)
+   the handling of SIGSTOP for a ptraced process has changed. Earlier
+   versions of the kernel would ignore these SIGSTOPs, while now
+   SIGSTOP is treated like any other signal, i.e. it is not muffled.
+   
+   If the gdb user does a 'continue' after the 'attach', gdb passes
+   the global variable stop_signal (which stores the signal from the
+   attach, SIGSTOP) to the ptrace(PTRACE_CONT,...)  call.  This is
+   problematic, because the kernel doesn't ignore such SIGSTOP
+   now. I.e. it is reported back to gdb, which in turn presents it
+   back to the user.
+ 
+   To avoid the problem, we use STOP_QUIETLY_NO_SIGSTOP, which allows
+   gdb to clear the value of stop_signal after the attach, so that it
+   is not passed back down to the kernel.  */
+
+enum stop_kind
+  {
+    NO_STOP_QUIETLY = 0,
+    STOP_QUIETLY,
+    STOP_QUIETLY_NO_SIGSTOP
+  };
+
+extern enum stop_kind stop_soon;

 
 /* Nonzero if proceed is being used for a "finish" command or a similar
    situation when stop_registers should be saved.  */
 
 /* Nonzero if proceed is being used for a "finish" command or a similar
    situation when stop_registers should be saved.  */


@@ -357,158 +418,17 @@ extern int proceed_to_finish;
    Thus this contains the return value from the called function (assuming
    values are returned in a register).  */
 
    Thus this contains the return value from the called function (assuming
    values are returned in a register).  */
 

-extern char *stop_registers;
+extern struct regcache *stop_registers;

 
 

-/* Nonzero if the child process in inferior_pid was attached rather
+/* Nonzero if the child process in inferior_ptid was attached rather

    than forked.  */
 
 extern int attach_flag;
 \f
    than forked.  */
 
 extern int attach_flag;
 \f

-/* Sigtramp is a routine that the kernel calls (which then calls the
-   signal handler).  On most machines it is a library routine that
-   is linked into the executable.
-
-   This macro, given a program counter value and the name of the
-   function in which that PC resides (which can be null if the
-   name is not known), returns nonzero if the PC and name show
-   that we are in sigtramp.
-
-   On most machines just see if the name is sigtramp (and if we have
-   no name, assume we are not in sigtramp).  */
-#if !defined (IN_SIGTRAMP)
-#if defined (SIGTRAMP_START)
-#define IN_SIGTRAMP(pc, name) \
-       ((pc) >= SIGTRAMP_START(pc)   \
-        && (pc) < SIGTRAMP_END(pc) \
-        )
-#else
-#define IN_SIGTRAMP(pc, name) \
-       (name && STREQ ("_sigtramp", name))
-#endif
-#endif
-\f

 /* Possible values for CALL_DUMMY_LOCATION.  */
 #define ON_STACK 1
 /* Possible values for CALL_DUMMY_LOCATION.  */
 #define ON_STACK 1

-#define BEFORE_TEXT_END 2
-#define AFTER_TEXT_END 3

 #define AT_ENTRY_POINT 4
 #define AT_ENTRY_POINT 4

-
-#if !defined (USE_GENERIC_DUMMY_FRAMES)
-#define USE_GENERIC_DUMMY_FRAMES 0
-#endif
-
-#if !defined (CALL_DUMMY_LOCATION)
-#define CALL_DUMMY_LOCATION ON_STACK
-#endif /* No CALL_DUMMY_LOCATION.  */
-
-#if !defined (CALL_DUMMY_ADDRESS)
-#define CALL_DUMMY_ADDRESS() (internal_error ("CALL_DUMMY_ADDRESS"), 0)
-#endif
-#if !defined (CALL_DUMMY_START_OFFSET)
-#define CALL_DUMMY_START_OFFSET (internal_error ("CALL_DUMMY_START_OFFSET"), 0)
-#endif
-#if !defined (CALL_DUMMY_BREAKPOINT_OFFSET)
-#define CALL_DUMMY_BREAKPOINT_OFFSET_P (0)
-#define CALL_DUMMY_BREAKPOINT_OFFSET (internal_error ("CALL_DUMMY_BREAKPOINT_OFFSET"), 0)
-#endif
-#if !defined CALL_DUMMY_BREAKPOINT_OFFSET_P
-#define CALL_DUMMY_BREAKPOINT_OFFSET_P (1)
-#endif
-#if !defined (CALL_DUMMY_LENGTH)
-#define CALL_DUMMY_LENGTH (internal_error ("CALL_DUMMY_LENGTH"), 0)
-#endif
-
-#if defined (CALL_DUMMY_STACK_ADJUST)
-#if !defined (CALL_DUMMY_STACK_ADJUST_P)
-#define CALL_DUMMY_STACK_ADJUST_P (1)
-#endif
-#endif
-#if !defined (CALL_DUMMY_STACK_ADJUST)
-#define CALL_DUMMY_STACK_ADJUST (internal_error ("CALL_DUMMY_STACK_ADJUST"), 0)
-#endif
-#if !defined (CALL_DUMMY_STACK_ADJUST_P)
-#define CALL_DUMMY_STACK_ADJUST_P (0)
-#endif
-
-/* FIXME: cagney/2000-04-17: gdbarch should manage this.  The default
-   shouldn't be necessary. */
-
-#if !defined (CALL_DUMMY_P)
-#if defined (CALL_DUMMY)
-#define CALL_DUMMY_P 1
-#else
-#define CALL_DUMMY_P 0
-#endif
-#endif
-
-#if !defined PUSH_DUMMY_FRAME
-#define PUSH_DUMMY_FRAME (internal_error ("PUSH_DUMMY_FRAME"), 0)
-#endif
-
-#if !defined FIX_CALL_DUMMY
-#define FIX_CALL_DUMMY(a1,a2,a3,a4,a5,a6,a7) (internal_error ("FIX_CALL_DUMMY"), 0)
-#endif
-
-#if !defined STORE_STRUCT_RETURN
-#define STORE_STRUCT_RETURN(a1,a2) (internal_error ("STORE_STRUCT_RETURN"), 0)
-#endif
-
-
-/* Are we in a call dummy? */
-
-extern int pc_in_call_dummy_before_text_end (CORE_ADDR pc, CORE_ADDR sp,
-                                            CORE_ADDR frame_address);
-#if !GDB_MULTI_ARCH
-#if !defined (PC_IN_CALL_DUMMY) && CALL_DUMMY_LOCATION == BEFORE_TEXT_END
-#define PC_IN_CALL_DUMMY(pc, sp, frame_address) pc_in_call_dummy_before_text_end (pc, sp, frame_address)
-#endif /* Before text_end.  */
-#endif
-
-extern int pc_in_call_dummy_after_text_end (CORE_ADDR pc, CORE_ADDR sp,
-                                           CORE_ADDR frame_address);
-#if !GDB_MULTI_ARCH
-#if !defined (PC_IN_CALL_DUMMY) && CALL_DUMMY_LOCATION == AFTER_TEXT_END
-#define PC_IN_CALL_DUMMY(pc, sp, frame_address) pc_in_call_dummy_after_text_end (pc, sp, frame_address)
-#endif
-#endif
-
-extern int pc_in_call_dummy_on_stack (CORE_ADDR pc, CORE_ADDR sp,
-                                     CORE_ADDR frame_address);
-#if !GDB_MULTI_ARCH
-#if !defined (PC_IN_CALL_DUMMY) && CALL_DUMMY_LOCATION == ON_STACK
-#define PC_IN_CALL_DUMMY(pc, sp, frame_address) pc_in_call_dummy_on_stack (pc, sp, frame_address)
-#endif
-#endif
-
-extern int pc_in_call_dummy_at_entry_point (CORE_ADDR pc, CORE_ADDR sp,
-                                           CORE_ADDR frame_address);
-#if !GDB_MULTI_ARCH
-#if !defined (PC_IN_CALL_DUMMY) && CALL_DUMMY_LOCATION == AT_ENTRY_POINT
-#define PC_IN_CALL_DUMMY(pc, sp, frame_address) pc_in_call_dummy_at_entry_point (pc, sp, frame_address)
-#endif
-#endif
-
-/* It's often not enough for our clients to know whether the PC is merely
-   somewhere within the call dummy.  They may need to know whether the
-   call dummy has actually completed.  (For example, wait_for_inferior
-   wants to know when it should truly stop because the call dummy has
-   completed.  If we're single-stepping because of slow watchpoints,
-   then we may find ourselves stopped at the entry of the call dummy,
-   and want to continue stepping until we reach the end.)
-
-   Note that this macro is intended for targets (like HP-UX) which
-   require more than a single breakpoint in their call dummies, and
-   therefore cannot use the CALL_DUMMY_BREAKPOINT_OFFSET mechanism.
-
-   If a target does define CALL_DUMMY_BREAKPOINT_OFFSET, then this
-   default implementation of CALL_DUMMY_HAS_COMPLETED is sufficient.
-   Else, a target may wish to supply an implementation that works in
-   the presense of multiple breakpoints in its call dummy.
- */
-#if !defined(CALL_DUMMY_HAS_COMPLETED)
-#define CALL_DUMMY_HAS_COMPLETED(pc, sp, frame_address) \
-  PC_IN_CALL_DUMMY((pc), (sp), (frame_address))
-#endif
+#define AT_SYMBOL 5

 
 /* If STARTUP_WITH_SHELL is set, GDB's "run"
    will attempts to start up the debugee under a shell.
 
 /* If STARTUP_WITH_SHELL is set, GDB's "run"
    will attempts to start up the debugee under a shell.