[RFA] Fix build failure [was Re: [RFC] fork in multi-threaded apps, per-thread pending_fork, other follow-fork cleanups.]

[Doug Evans <dje at google dot com>]

On Sun, May 24, 2009 at 11:01 AM, Pedro Alves <pedro@codesourcery.com> wrote:
> [...]
> We're not worse than before, so I checked in this revision of that
> patch with a few extra comments and small cleanups.
>
> --
> Pedro Alves
>
> gdb/
> 2009-05-24 ?Pedro Alves ?<pedro@codesourcery.com>
>
> ? ? ? ?* gdbthread.h (struct thread_info): New `pending_follow' field.
> ? ? ? ?* thread.c (new_thread): New function.
> ? ? ? ?(add_thread_silent): Use it.
> ? ? ? ?* breakpoint.c (internal_breakpoint_number): New global, moved
> ? ? ? ?from inside...
> ? ? ? ?(create_internal_breakpoint): ... this.
> ? ? ? ?(clone_momentary_breakpoint): New.
> ? ? ? ?* breakpoint.h (clone_momentary_breakpoint): Declare.
> ? ? ? ?* infrun.c (nullify_last_target_wait_ptid): Move declaration
> ? ? ? ?higher.
> ? ? ? ?(pending_follow): Delete.
> ? ? ? ?(follow_fork): Handle pending follow fork event here. ?Moved the
> ? ? ? ?preserving of thread stepping state here.
> ? ? ? ?(resume): Don't handle pending follow fork events here. ?Only
> ? ? ? ?install the inferior's terminal modes if we're about to resume it.
> ? ? ? ?(proceed): Handle possible pending follow fork events here.
> ? ? ? ?(init_wait_for_inferior): No need to clear pending_follow anymore,
> ? ? ? ?it's gone.
> ? ? ? ?(handle_inferior_event): Adjust to per-thread `pending_follow'.
> ? ? ? ?Call `follow_fork' to handle following the fork. ?If the
> ? ? ? ?follow-fork is cancelled, stop stepping.
> ? ? ? ?* linux-nat.c (linux_child_follow_fork): Adjust to per-thread
> ? ? ? ?`pending_follow' events. ?Remove code that handled preserving the
> ? ? ? ?thread stepping state.
> ? ? ? ?* inf-ptrace.c (inf_ptrace_follow_fork): Ditto.
> ? ? ? ?* inf-ttrace.c (inf_ttrace_follow_fork): Ditto.
>
> gdb/testsuite/
> 2009-05-24 ?Pedro Alves ?<pedro@codesourcery.com>
>
> ? ? ? ?* gdb.threads/fork-thread-pending.c: New.
> ? ? ? ?* gdb.threads/fork-thread-pending.exp: New.
>
> ---
> ?gdb/breakpoint.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ? 40 +++
> ?gdb/breakpoint.h ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ? ?2
> ?gdb/gdbthread.h ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | ? ?5
> ?gdb/inf-ptrace.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ? 36 ---
> ?gdb/inf-ttrace.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ? 44 ----
> ?gdb/infrun.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ?241 ++++++++++++++++------
> ?gdb/linux-nat.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | ? 37 ---
> ?gdb/testsuite/gdb.threads/fork-thread-pending.c ? | ?109 +++++++++
> ?gdb/testsuite/gdb.threads/fork-thread-pending.exp | ?128 +++++++++++
> ?gdb/thread.c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?| ? 37 ++-
> ?10 files changed, 508 insertions(+), 171 deletions(-)
>
> Index: src/gdb/gdbthread.h
> ===================================================================
> --- src.orig/gdb/gdbthread.h ? ?2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/gdbthread.h 2009-05-24 17:09:03.000000000 +0100
> @@ -165,6 +165,11 @@ struct thread_info
> ? ? ?next time inferior stops if it stops due to stepping. ?*/
> ? int step_multi;
>
> + ?/* This is used to remember when a fork or vfork event was caught by
> + ? ? a catchpoint, and thus the event is to be followed at the next
> + ? ? resume of the thread, and not immediately. ?*/
> + ?struct target_waitstatus pending_follow;
> +
> ? /* Last signal that the inferior received (why it stopped). ?*/
> ? enum target_signal stop_signal;
>
> Index: src/gdb/thread.c
> ===================================================================
> --- src.orig/gdb/thread.c ? ? ? 2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/thread.c ? ?2009-05-24 17:14:18.000000000 +0100
> @@ -141,6 +141,28 @@ init_thread_list (void)
> ? thread_list = NULL;
> ?}
>
> +/* Allocate a new thread with target id PTID and add it to the thread
> + ? list. ?*/
> +
> +static struct thread_info *
> +new_thread (ptid_t ptid)
> +{
> + ?struct thread_info *tp;
> +
> + ?tp = xcalloc (1, sizeof (*tp));
> +
> + ?tp->ptid = ptid;
> + ?tp->num = ++highest_thread_num;
> + ?tp->next = thread_list;
> + ?thread_list = tp;
> +
> + ?/* Nothing to follow yet. ?*/
> + ?tp->pending_follow.kind = TARGET_WAITKIND_SPURIOUS;
> + ?tp->state_ = THREAD_STOPPED;
> +
> + ?return tp;
> +}
> +
> ?struct thread_info *
> ?add_thread_silent (ptid_t ptid)
> ?{
> @@ -162,12 +184,7 @@ add_thread_silent (ptid_t ptid)
>
> ? ? ? if (ptid_equal (inferior_ptid, ptid))
> ? ? ? ?{
> - ? ? ? ? tp = xmalloc (sizeof (*tp));
> - ? ? ? ? memset (tp, 0, sizeof (*tp));
> - ? ? ? ? tp->ptid = minus_one_ptid;
> - ? ? ? ? tp->num = ++highest_thread_num;
> - ? ? ? ? tp->next = thread_list;
> - ? ? ? ? thread_list = tp;
> + ? ? ? ? tp = new_thread (ptid);
>
> ? ? ? ? ?/* Make switch_to_thread not read from the thread. ?*/
> ? ? ? ? ?tp->state_ = THREAD_EXITED;
> @@ -191,13 +208,7 @@ add_thread_silent (ptid_t ptid)
> ? ? ? ?delete_thread (ptid);
> ? ? }
>
> - ?tp = (struct thread_info *) xmalloc (sizeof (*tp));
> - ?memset (tp, 0, sizeof (*tp));
> - ?tp->ptid = ptid;
> - ?tp->num = ++highest_thread_num;
> - ?tp->next = thread_list;
> - ?thread_list = tp;
> -
> + ?tp = new_thread (ptid);
> ? observer_notify_new_thread (tp);
>
> ? return tp;
> Index: src/gdb/breakpoint.c
> ===================================================================
> --- src.orig/gdb/breakpoint.c ? 2009-05-23 18:24:43.000000000 +0100
> +++ src/gdb/breakpoint.c ? ? ? ?2009-05-24 17:18:54.000000000 +0100
> @@ -1456,10 +1456,11 @@ reattach_breakpoints (int pid)
> ? return 0;
> ?}
>
> +static int internal_breakpoint_number = -1;
> +
> ?static struct breakpoint *
> ?create_internal_breakpoint (CORE_ADDR address, enum bptype type)
> ?{
> - ?static int internal_breakpoint_number = -1;
> ? struct symtab_and_line sal;
> ? struct breakpoint *b;
>
> @@ -5007,6 +5008,43 @@ set_momentary_breakpoint (struct symtab_
> ? return b;
> ?}
>
> +/* Make a deep copy of momentary breakpoint ORIG. ?Returns NULL if
> + ? ORIG is NULL. ?*/
> +
> +struct breakpoint *
> +clone_momentary_breakpoint (struct breakpoint *orig)
> +{
> + ?struct breakpoint *copy;
> +
> + ?/* If there's nothing to clone, then return nothing. ?*/
> + ?if (orig == NULL)
> + ? ?return NULL;
> +
> + ?copy = set_raw_breakpoint_without_location (orig->type);
> + ?copy->loc = allocate_bp_location (copy);
> + ?set_breakpoint_location_function (copy->loc);
> +
> + ?copy->loc->requested_address = orig->loc->requested_address;
> + ?copy->loc->address = orig->loc->address;
> + ?copy->loc->section = orig->loc->section;
> +
> + ?if (orig->source_file == NULL)
> + ? ?copy->source_file = NULL;
> + ?else
> + ? ?copy->source_file = xstrdup (orig->source_file);
> +
> + ?copy->line_number = orig->line_number;
> + ?copy->frame_id = orig->frame_id;
> + ?copy->thread = orig->thread;
> +
> + ?copy->enable_state = bp_enabled;
> + ?copy->disposition = disp_donttouch;
> + ?copy->number = internal_breakpoint_number--;
> +
> + ?update_global_location_list_nothrow (0);
> + ?return copy;
> +}
> +
> ?struct breakpoint *
> ?set_momentary_breakpoint_at_pc (CORE_ADDR pc, enum bptype type)
> ?{
> Index: src/gdb/breakpoint.h
> ===================================================================
> --- src.orig/gdb/breakpoint.h ? 2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/breakpoint.h ? ? ? ?2009-05-24 17:09:03.000000000 +0100
> @@ -696,6 +696,8 @@ extern struct breakpoint *set_momentary_
> ?extern struct breakpoint *set_momentary_breakpoint_at_pc
> ? (CORE_ADDR pc, enum bptype type);
>
> +extern struct breakpoint *clone_momentary_breakpoint (struct breakpoint *bpkt);
> +
> ?extern void set_ignore_count (int, int, int);
>
> ?extern void set_default_breakpoint (int, CORE_ADDR, struct symtab *, int);
> Index: src/gdb/infrun.c
> ===================================================================
> --- src.orig/gdb/infrun.c ? ? ? 2009-05-24 17:02:20.000000000 +0100
> +++ src/gdb/infrun.c ? ?2009-05-24 17:13:31.000000000 +0100
> @@ -83,6 +83,8 @@ static int prepare_to_proceed (int);
>
> ?void _initialize_infrun (void);
>
> +void nullify_last_target_wait_ptid (void);
> +
> ?/* 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. ?*/
> @@ -255,21 +257,6 @@ void init_thread_stepping_state (struct
>
> ?void init_infwait_state (void);
>
> -/* This is used to remember when a fork or vfork event was caught by a
> - ? catchpoint, and thus the event is to be followed at the next resume
> - ? of the inferior, and not immediately. ?*/
> -static struct
> -{
> - ?enum target_waitkind kind;
> - ?struct
> - ?{
> - ? ?ptid_t parent_pid;
> - ? ?ptid_t child_pid;
> - ?}
> - ?fork_event;
> -}
> -pending_follow;
> -
> ?static const char follow_fork_mode_child[] = "child";
> ?static const char follow_fork_mode_parent[] = "parent";
>
> @@ -290,12 +277,157 @@ Debugger response to a program call of f
> ?}
>
>
> +/* Tell the target to follow the fork we're stopped at. ?Returns true
> + ? if the inferior should be resumed; false, if the target for some
> + ? reason decided it's best not to resume. ?*/
> +
> ?static int
> ?follow_fork (void)
> ?{
> ? int follow_child = (follow_fork_mode_string == follow_fork_mode_child);
> + ?int should_resume = 1;
> + ?struct thread_info *tp;
> +
> + ?/* Copy user stepping state to the new inferior thread. ?FIXME: the
> + ? ? followed fork child thread should have a copy of most of the
> + ? ? parent thread structure's run control related fields, not just
> + ? ? these. ?*/
> + ?struct breakpoint *step_resume_breakpoint;
> + ?CORE_ADDR step_range_start;
> + ?CORE_ADDR step_range_end;
> + ?struct frame_id step_frame_id;
> +
> + ?if (!non_stop)
> + ? ?{
> + ? ? ?ptid_t wait_ptid;
> + ? ? ?struct target_waitstatus wait_status;
> +
> + ? ? ?/* Get the last target status returned by target_wait(). ?*/
> + ? ? ?get_last_target_status (&wait_ptid, &wait_status);
> +
> + ? ? ?/* If not stopped at a fork event, then there's nothing else to
> + ? ? ? ?do. ?*/
> + ? ? ?if (wait_status.kind != TARGET_WAITKIND_FORKED
> + ? ? ? ? && wait_status.kind != TARGET_WAITKIND_VFORKED)
> + ? ? ? return 1;
> +
> + ? ? ?/* Check if we switched over from WAIT_PTID, since the event was
> + ? ? ? ?reported. ?*/
> + ? ? ?if (!ptid_equal (wait_ptid, minus_one_ptid)
> + ? ? ? ? && !ptid_equal (inferior_ptid, wait_ptid))
> + ? ? ? {
> + ? ? ? ? /* We did. ?Switch back to WAIT_PTID thread, to tell the
> + ? ? ? ? ? ?target to follow it (in either direction). ?We'll
> + ? ? ? ? ? ?afterwards refuse to resume, and inform the user what
> + ? ? ? ? ? ?happened. ?*/
> + ? ? ? ? switch_to_thread (wait_ptid);
> + ? ? ? ? should_resume = 0;
> + ? ? ? }
> + ? ?}
> +
> + ?tp = inferior_thread ();
> +
> + ?/* If there were any forks/vforks that were caught and are now to be
> + ? ? followed, then do so now. ?*/
> + ?switch (tp->pending_follow.kind)
> + ? ?{
> + ? ?case TARGET_WAITKIND_FORKED:
> + ? ?case TARGET_WAITKIND_VFORKED:
> + ? ? ?{
> + ? ? ? ptid_t parent, child;
> +
> + ? ? ? /* If the user did a next/step, etc, over a fork call,
> + ? ? ? ? ?preserve the stepping state in the fork child. ?*/
> + ? ? ? if (follow_child && should_resume)
> + ? ? ? ? {
> + ? ? ? ? ? step_resume_breakpoint
> + ? ? ? ? ? ? = clone_momentary_breakpoint (tp->step_resume_breakpoint);
> + ? ? ? ? ? step_range_start = tp->step_range_start;
> + ? ? ? ? ? step_range_end = tp->step_range_end;
> + ? ? ? ? ? step_frame_id = tp->step_frame_id;
> +
> + ? ? ? ? ? /* For now, delete the parent's sr breakpoint, otherwise,
> + ? ? ? ? ? ? ?parent/child sr breakpoints are considered duplicates,
> + ? ? ? ? ? ? ?and the child version will not be installed. ?Remove
> + ? ? ? ? ? ? ?this when the breakpoints module becomes aware of
> + ? ? ? ? ? ? ?inferiors and address spaces. ?*/
> + ? ? ? ? ? delete_step_resume_breakpoint (tp);
> + ? ? ? ? ? tp->step_range_start = 0;
> + ? ? ? ? ? tp->step_range_end = 0;
> + ? ? ? ? ? tp->step_frame_id = null_frame_id;
> + ? ? ? ? }
> +
> + ? ? ? parent = inferior_ptid;
> + ? ? ? child = tp->pending_follow.value.related_pid;
> +
> + ? ? ? /* Tell the target to do whatever is necessary to follow
> + ? ? ? ? ?either parent or child. ?*/
> + ? ? ? if (target_follow_fork (follow_child))
> + ? ? ? ? {
> + ? ? ? ? ? /* Target refused to follow, or there's some other reason
> + ? ? ? ? ? ? ?we shouldn't resume. ?*/
> + ? ? ? ? ? should_resume = 0;
> + ? ? ? ? }
> + ? ? ? else
> + ? ? ? ? {
> + ? ? ? ? ? /* This pending follow fork event is now handled, one way
> + ? ? ? ? ? ? ?or another. ?The previous selected thread may be gone
> + ? ? ? ? ? ? ?from the lists by now, but if it is still around, need
> + ? ? ? ? ? ? ?to clear the pending follow request. ?*/
> + ? ? ? ? ? tp = find_thread_pid (parent);
> + ? ? ? ? ? if (tp)
> + ? ? ? ? ? ? tp->pending_follow.kind = TARGET_WAITKIND_SPURIOUS;
> +
> + ? ? ? ? ? /* This makes sure we don't try to apply the "Switched
> + ? ? ? ? ? ? ?over from WAIT_PID" logic above. ?*/
> + ? ? ? ? ? nullify_last_target_wait_ptid ();
> +
> + ? ? ? ? ? /* If we followed the child, switch to it... */
> + ? ? ? ? ? if (follow_child)
> + ? ? ? ? ? ? {
> + ? ? ? ? ? ? ? switch_to_thread (child);
> +
> + ? ? ? ? ? ? ? /* ... and preserve the stepping state, in case the
> + ? ? ? ? ? ? ? ? ?user was stepping over the fork call. ?*/
> + ? ? ? ? ? ? ? if (should_resume)
> + ? ? ? ? ? ? ? ? {
> + ? ? ? ? ? ? ? ? ? tp = inferior_thread ();
> + ? ? ? ? ? ? ? ? ? tp->step_resume_breakpoint = step_resume_breakpoint;
> + ? ? ? ? ? ? ? ? ? tp->step_range_start = step_range_start;
> + ? ? ? ? ? ? ? ? ? tp->step_range_end = step_range_end;
> + ? ? ? ? ? ? ? ? ? tp->step_frame_id = step_frame_id;
> + ? ? ? ? ? ? ? ? }
> + ? ? ? ? ? ? ? else
> + ? ? ? ? ? ? ? ? {
> + ? ? ? ? ? ? ? ? ? /* If we get here, it was because we're trying to
> + ? ? ? ? ? ? ? ? ? ? ?resume from a fork catchpoint, but, the user
> + ? ? ? ? ? ? ? ? ? ? ?has switched threads away from the thread that
> + ? ? ? ? ? ? ? ? ? ? ?forked. ?In that case, the resume command
> + ? ? ? ? ? ? ? ? ? ? ?issued is most likely not applicable to the
> + ? ? ? ? ? ? ? ? ? ? ?child, so just warn, and refuse to resume. ?*/
> + ? ? ? ? ? ? ? ? ? warning (_("\
> +Not resuming: switched threads before following fork child.\n"));
> + ? ? ? ? ? ? ? ? }
> +
> + ? ? ? ? ? ? ? /* Reset breakpoints in the child as appropriate. ?*/
> + ? ? ? ? ? ? ? follow_inferior_reset_breakpoints ();
> + ? ? ? ? ? ? }
> + ? ? ? ? ? else
> + ? ? ? ? ? ? switch_to_thread (parent);
> + ? ? ? ? }
> + ? ? ?}
> + ? ? ?break;
> + ? ?case TARGET_WAITKIND_SPURIOUS:
> + ? ? ?/* Nothing to follow. ?*/
> + ? ? ?break;
> + ? ?default:
> + ? ? ?internal_error (__FILE__, __LINE__,
> + ? ? ? ? ? ? ? ? ? ? "Unexpected pending_follow.kind %d\n",
> + ? ? ? ? ? ? ? ? ? ? tp->pending_follow.kind);
> + ? ? ?break;
> + ? ?}
>
> - ?return target_follow_fork (follow_child);
> + ?return should_resume;
> ?}
>
> ?void
> @@ -987,8 +1119,6 @@ resume (int step, enum target_signal sig
> ?{
> ? int should_resume = 1;
> ? struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
> -
> - ?/* Note that these must be reset if we follow a fork below. ?*/
> ? struct regcache *regcache = get_current_regcache ();
> ? struct gdbarch *gdbarch = get_regcache_arch (regcache);
> ? struct thread_info *tp = inferior_thread ();
> @@ -1058,31 +1188,6 @@ a command like `return' or `jump' to con
> ? if (step)
> ? ? step = maybe_software_singlestep (gdbarch, pc);
>
> - ?/* If there were any forks/vforks/execs that were caught and are
> - ? ? now to be followed, then do so. ?*/
> - ?switch (pending_follow.kind)
> - ? ?{
> - ? ?case TARGET_WAITKIND_FORKED:
> - ? ?case TARGET_WAITKIND_VFORKED:
> - ? ? ?pending_follow.kind = TARGET_WAITKIND_SPURIOUS;
> - ? ? ?if (follow_fork ())
> - ? ? ? should_resume = 0;
> -
> - ? ? ?/* Following a child fork will change our notion of current
> - ? ? ? ?thread. ?*/
> - ? ? ?tp = inferior_thread ();
> - ? ? ?regcache = get_current_regcache ();
> - ? ? ?gdbarch = get_regcache_arch (regcache);
> - ? ? ?pc = regcache_read_pc (regcache);
> - ? ? ?break;
> -
> - ? ?default:
> - ? ? ?break;
> - ? ?}
> -
> - ?/* Install inferior's terminal modes. ?*/
> - ?target_terminal_inferior ();
> -
> ? if (should_resume)
> ? ? {
> ? ? ? ptid_t resume_ptid;
> @@ -1164,6 +1269,9 @@ a command like `return' or `jump' to con
> ? ? ? ? ? displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
> ? ? ? ? }
>
> + ? ? ?/* Install inferior's terminal modes. ?*/
> + ? ? ?target_terminal_inferior ();
> +
> ? ? ? /* Avoid confusing the next resume, if the next stop/resume
> ? ? ? ? happens to apply to another thread. ?*/
> ? ? ? tp->stop_signal = TARGET_SIGNAL_0;
> @@ -1305,12 +1413,26 @@ prepare_to_proceed (int step)
> ?void
> ?proceed (CORE_ADDR addr, enum target_signal siggnal, int step)
> ?{
> - ?struct regcache *regcache = get_current_regcache ();
> - ?struct gdbarch *gdbarch = get_regcache_arch (regcache);
> + ?struct regcache *regcache;
> + ?struct gdbarch *gdbarch;
> ? struct thread_info *tp;
> - ?CORE_ADDR pc = regcache_read_pc (regcache);
> + ?CORE_ADDR pc;
> ? int oneproc = 0;
>
> + ?/* If we're stopped at a fork/vfork, follow the branch set by the
> + ? ? "set follow-fork-mode" command; otherwise, we'll just proceed
> + ? ? resuming the current thread. ?*/
> + ?if (!follow_fork ())
> + ? ?{
> + ? ? ?/* The target for some reason decided not to resume. ?*/
> + ? ? ?normal_stop ();
> + ? ? ?return;
> + ? ?}
> +
> + ?regcache = get_current_regcache ();
> + ?gdbarch = get_regcache_arch (regcache);
> + ?pc = regcache_read_pc (regcache);
> +
> ? if (step > 0)
> ? ? step_start_function = find_pc_function (pc);
> ? if (step < 0)
> @@ -1517,9 +1639,6 @@ init_wait_for_inferior (void)
>
> ? breakpoint_init_inferior (inf_starting);
>
> - ?/* The first resume is not following a fork/vfork/exec. */
> - ?pending_follow.kind = TARGET_WAITKIND_SPURIOUS; ? ? ?/* I.e., none. */
> -
> ? clear_proceed_status ();
>
> ? stepping_past_singlestep_breakpoint = 0;
> @@ -1698,8 +1817,6 @@ infrun_thread_stop_requested (ptid_t pti
> ? iterate_over_threads (infrun_thread_stop_requested_callback, &ptid);
> ?}
>
> -void nullify_last_target_wait_ptid (void);
> -
> ?static void
> ?infrun_thread_thread_exit (struct thread_info *tp, int silent)
> ?{
> @@ -2407,10 +2524,6 @@ handle_inferior_event (struct execution_
> ? ? case TARGET_WAITKIND_VFORKED:
> ? ? ? if (debug_infrun)
> ? ? ? ? fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_FORKED\n");
> - ? ? ?pending_follow.kind = ecs->ws.kind;
> -
> - ? ? ?pending_follow.fork_event.parent_pid = ecs->ptid;
> - ? ? ?pending_follow.fork_event.child_pid = ecs->ws.value.related_pid;
>
> ? ? ? if (!ptid_equal (ecs->ptid, inferior_ptid))
> ? ? ? ?{
> @@ -2439,6 +2552,11 @@ handle_inferior_event (struct execution_
> ? ? ? ? ?detach_breakpoints (child_pid);
> ? ? ? ?}
>
> + ? ? ?/* In case the event is caught by a catchpoint, remember that
> + ? ? ? ?the event is to be followed at the next resume of the thread,
> + ? ? ? ?and not immediately. ?*/
> + ? ? ?ecs->event_thread->pending_follow = ecs->ws;
> +
> ? ? ? stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));
>
> ? ? ? ecs->event_thread->stop_bpstat = bpstat_stop_status (stop_pc, ecs->ptid);
> @@ -2448,8 +2566,19 @@ handle_inferior_event (struct execution_
> ? ? ? /* If no catchpoint triggered for this, then keep going. ?*/
> ? ? ? if (ecs->random_signal)
> ? ? ? ?{
> + ? ? ? ? int should_resume;
> +
> ? ? ? ? ?ecs->event_thread->stop_signal = TARGET_SIGNAL_0;
> - ? ? ? ? keep_going (ecs);
> +
> + ? ? ? ? should_resume = follow_fork ();
> +
> + ? ? ? ? ecs->event_thread = inferior_thread ();
> + ? ? ? ? ecs->ptid = inferior_ptid;
> +
> + ? ? ? ? if (should_resume)
> + ? ? ? ? ? keep_going (ecs);
> + ? ? ? ? else
> + ? ? ? ? ? stop_stepping (ecs);
> ? ? ? ? ?return;
> ? ? ? ?}
> ? ? ? ecs->event_thread->stop_signal = TARGET_SIGNAL_TRAP;
> Index: src/gdb/linux-nat.c
> ===================================================================
> --- src.orig/gdb/linux-nat.c ? ?2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/linux-nat.c 2009-05-24 17:09:03.000000000 +0100
> @@ -575,19 +575,17 @@ static int
> ?linux_child_follow_fork (struct target_ops *ops, int follow_child)
> ?{
> ? sigset_t prev_mask;
> - ?ptid_t last_ptid;
> - ?struct target_waitstatus last_status;
> ? int has_vforked;
> ? int parent_pid, child_pid;
>
> ? block_child_signals (&prev_mask);
>
> - ?get_last_target_status (&last_ptid, &last_status);
> - ?has_vforked = (last_status.kind == TARGET_WAITKIND_VFORKED);
> - ?parent_pid = ptid_get_lwp (last_ptid);
> + ?has_vforked = (inferior_thread ()->pending_follow.kind
> + ? ? ? ? ? ? ? ?== TARGET_WAITKIND_VFORKED);
> + ?parent_pid = ptid_get_lwp (inferior_ptid);
> ? if (parent_pid == 0)
> - ? ?parent_pid = ptid_get_pid (last_ptid);
> - ?child_pid = PIDGET (last_status.value.related_pid);
> + ? ?parent_pid = ptid_get_pid (inferior_ptid);
> + ?child_pid = PIDGET (inferior_thread ()->pending_follow.value.related_pid);
>
> ? if (! follow_child)
> ? ? {
> @@ -625,7 +623,7 @@ linux_child_follow_fork (struct target_o
> ? ? ? ? ?/* Add process to GDB's tables. ?*/
> ? ? ? ? ?child_inf = add_inferior (child_pid);
>
> - ? ? ? ? parent_inf = find_inferior_pid (GET_PID (last_ptid));
> + ? ? ? ? parent_inf = current_inferior ();
> ? ? ? ? ?child_inf->attach_flag = parent_inf->attach_flag;
> ? ? ? ? ?copy_terminal_info (child_inf, parent_inf);
>
> @@ -692,21 +690,9 @@ linux_child_follow_fork (struct target_o
> ? ? }
> ? else
> ? ? {
> - ? ? ?struct thread_info *last_tp = find_thread_pid (last_ptid);
> ? ? ? struct thread_info *tp;
> - ? ? ?char child_pid_spelling[40];
> ? ? ? struct inferior *parent_inf, *child_inf;
>
> - ? ? ?/* Copy user stepping state to the new inferior thread. ?*/
> - ? ? ?struct breakpoint *step_resume_breakpoint = last_tp->step_resume_breakpoint;
> - ? ? ?CORE_ADDR step_range_start = last_tp->step_range_start;
> - ? ? ?CORE_ADDR step_range_end = last_tp->step_range_end;
> - ? ? ?struct frame_id step_frame_id = last_tp->step_frame_id;
> -
> - ? ? ?/* Otherwise, deleting the parent would get rid of this
> - ? ? ? ?breakpoint. ?*/
> - ? ? ?last_tp->step_resume_breakpoint = NULL;
> -
> ? ? ? /* Before detaching from the parent, remove all breakpoints from it. */
> ? ? ? remove_breakpoints ();
>
> @@ -723,7 +709,7 @@ linux_child_follow_fork (struct target_o
>
> ? ? ? child_inf = add_inferior (child_pid);
>
> - ? ? ?parent_inf = find_inferior_pid (GET_PID (last_ptid));
> + ? ? ?parent_inf = current_inferior ();
> ? ? ? child_inf->attach_flag = parent_inf->attach_flag;
> ? ? ? copy_terminal_info (child_inf, parent_inf);
>
> @@ -772,15 +758,6 @@ linux_child_follow_fork (struct target_o
>
> ? ? ? linux_nat_switch_fork (inferior_ptid);
> ? ? ? check_for_thread_db ();
> -
> - ? ? ?tp = inferior_thread ();
> - ? ? ?tp->step_resume_breakpoint = step_resume_breakpoint;
> - ? ? ?tp->step_range_start = step_range_start;
> - ? ? ?tp->step_range_end = step_range_end;
> - ? ? ?tp->step_frame_id = step_frame_id;
> -
> - ? ? ?/* Reset breakpoints in the child as appropriate. ?*/
> - ? ? ?follow_inferior_reset_breakpoints ();
> ? ? }
>
> ? restore_child_signals_mask (&prev_mask);
> Index: src/gdb/inf-ptrace.c
> ===================================================================
> --- src.orig/gdb/inf-ptrace.c ? 2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/inf-ptrace.c ? ? ? ?2009-05-24 18:20:14.000000000 +0100
> @@ -46,20 +46,8 @@ inf_ptrace_follow_fork (struct target_op
> ?{
> ? pid_t pid, fpid;
> ? ptrace_state_t pe;
> - ?struct thread_info *last_tp = NULL;
>
> - ?/* FIXME: kettenis/20050720: This stuff should really be passed as
> - ? ? an argument by our caller. ?*/
> - ?{
> - ? ?ptid_t ptid;
> - ? ?struct target_waitstatus status;
> -
> - ? ?get_last_target_status (&ptid, &status);
> - ? ?gdb_assert (status.kind == TARGET_WAITKIND_FORKED);
> -
> - ? ?pid = ptid_get_pid (ptid);
> - ? ?last_tp = find_thread_pid (ptid);
> - ?}
> + ?pid = ptid_get_pid (inferior_ptid);
>
> ? if (ptrace (PT_GET_PROCESS_STATE, pid,
> ? ? ? ? ? ? ? (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
> @@ -70,18 +58,9 @@ inf_ptrace_follow_fork (struct target_op
>
> ? if (follow_child)
> ? ? {
> - ? ? ?/* Copy user stepping state to the new inferior thread. ?*/
> - ? ? ?struct breakpoint *step_resume_breakpoint = last_tp->step_resume_breakpoint;
> - ? ? ?CORE_ADDR step_range_start = last_tp->step_range_start;
> - ? ? ?CORE_ADDR step_range_end = last_tp->step_range_end;
> - ? ? ?struct frame_id step_frame_id = last_tp->step_frame_id;
> ? ? ? struct inferior *parent_inf, *child_inf;
> ? ? ? struct thread_info *tp;
>
> - ? ? ?/* Otherwise, deleting the parent would get rid of this
> - ? ? ? ?breakpoint. ?*/
> - ? ? ?last_tp->step_resume_breakpoint = NULL;
> -
> ? ? ? parent_inf = find_inferior_pid (pid);
>
> ? ? ? /* Add the child. ?*/
> @@ -102,26 +81,15 @@ inf_ptrace_follow_fork (struct target_op
> ? ? ? /* Delete the parent. ?*/
> ? ? ? detach_inferior (pid);
>
> - ? ? ?tp = add_thread_silent (inferior_ptid);
> -
> - ? ? ?tp->step_resume_breakpoint = step_resume_breakpoint;
> - ? ? ?tp->step_range_start = step_range_start;
> - ? ? ?tp->step_range_end = step_range_end;
> - ? ? ?tp->step_frame_id = step_frame_id;
> -
> - ? ? ?/* Reset breakpoints in the child as appropriate. ?*/
> - ? ? ?follow_inferior_reset_breakpoints ();
> + ? ? ?add_thread_silent (inferior_ptid);
> ? ? }
> ? else
> ? ? {
> - ? ? ?inferior_ptid = pid_to_ptid (pid);
> -
> ? ? ? /* Breakpoints have already been detached from the child by
> ? ? ? ? infrun.c. ?*/
>
> ? ? ? if (ptrace (PT_DETACH, fpid, (PTRACE_TYPE_ARG3)1, 0) == -1)
> ? ? ? ?perror_with_name (("ptrace"));
> - ? ? ?detach_inferior (pid);
> ? ? }
>
> ? return 0;
> Index: src/gdb/inf-ttrace.c
> ===================================================================
> --- src.orig/gdb/inf-ttrace.c ? 2009-05-21 23:45:24.000000000 +0100
> +++ src/gdb/inf-ttrace.c ? ? ? ?2009-05-24 17:09:03.000000000 +0100
> @@ -412,25 +412,13 @@ inf_ttrace_follow_fork (struct target_op
> ? pid_t pid, fpid;
> ? lwpid_t lwpid, flwpid;
> ? ttstate_t tts;
> - ?struct thread_info *last_tp = NULL;
> - ?struct breakpoint *step_resume_breakpoint = NULL;
> - ?CORE_ADDR step_range_start = 0, step_range_end = 0;
> - ?struct frame_id step_frame_id = null_frame_id;
> -
> - ?/* FIXME: kettenis/20050720: This stuff should really be passed as
> - ? ? an argument by our caller. ?*/
> - ?{
> - ? ?ptid_t ptid;
> - ? ?struct target_waitstatus status;
> -
> - ? ?get_last_target_status (&ptid, &status);
> - ? ?gdb_assert (status.kind == TARGET_WAITKIND_FORKED
> - ? ? ? ? ? ? ? || status.kind == TARGET_WAITKIND_VFORKED);
> -
> - ? ?pid = ptid_get_pid (ptid);
> - ? ?lwpid = ptid_get_lwp (ptid);
> - ? ?last_tp = find_thread_pid (ptid);
> - ?}
> + ?struct thread_info *tp = inferior_thread ();
> +
> + ?gdb_assert (tp->pending_follow.kind == TARGET_WAITKIND_FORKED
> + ? ? ? ? ? ? || tp->pending_follow.kind == TARGET_WAITKIND_VFORKED);
> +
> + ?pid = ptid_get_pid (inferior_ptid);
> + ?lwpid = ptid_get_lwp (inferior_ptid);
>
> ? /* Get all important details that core GDB doesn't (and shouldn't)
> ? ? ?know about. ?*/
> @@ -462,16 +450,6 @@ inf_ttrace_follow_fork (struct target_op
>
> ? ? ? parent_inf = find_inferior_pid (pid);
>
> - ? ? ?/* Copy user stepping state to the new inferior thread. ?*/
> - ? ? ?step_resume_breakpoint = last_tp->step_resume_breakpoint;
> - ? ? ?step_range_start = last_tp->step_range_start;
> - ? ? ?step_range_end = last_tp->step_range_end;
> - ? ? ?step_frame_id = last_tp->step_frame_id;
> -
> - ? ? ?/* Otherwise, deleting the parent would get rid of this
> - ? ? ? ?breakpoint. ?*/
> - ? ? ?last_tp->step_resume_breakpoint = NULL;
> -
> ? ? ? inferior_ptid = ptid_build (fpid, flwpid, 0);
> ? ? ? inf = add_inferior (fpid);
> ? ? ? inf->attach_flag = parent_inf->attach_flag;
> @@ -553,14 +531,6 @@ Detaching after fork from child process
> ? ? ? ?xmalloc (sizeof (struct inf_ttrace_private_thread_info));
> ? ? ? memset (ti->private, 0,
> ? ? ? ? ? ? ?sizeof (struct inf_ttrace_private_thread_info));
> -
> - ? ? ?ti->step_resume_breakpoint = step_resume_breakpoint;
> - ? ? ?ti->step_range_start = step_range_start;
> - ? ? ?ti->step_range_end = step_range_end;
> - ? ? ?ti->step_frame_id = step_frame_id;
> -
> - ? ? ?/* Reset breakpoints in the child as appropriate. ?*/
> - ? ? ?follow_inferior_reset_breakpoints ();
> ? ? }
>
> ? return 0;
> Index: src/gdb/testsuite/gdb.threads/fork-thread-pending.c
> ===================================================================
> --- /dev/null ? 1970-01-01 00:00:00.000000000 +0000
> +++ src/gdb/testsuite/gdb.threads/fork-thread-pending.c 2009-05-24 17:09:03.000000000 +0100
> @@ -0,0 +1,109 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + ? Copyright 2008, 2009 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/>. ?*/
> +
> +#include <pthread.h>
> +#include <assert.h>
> +#include <unistd.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <errno.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +
> +#define NUMTHREADS 10
> +
> +volatile int done = 0;
> +
> +static void *
> +start (void *arg)
> +{
> + ?while (!done)
> + ? ?usleep (100);
> + ?assert (0);
> + ?return arg;
> +}
> +
> +void *
> +thread_function (void *arg)
> +{
> + ?int x = * (int *) arg;
> +
> + ?printf ("Thread <%d> executing\n", x);
> +
> + ?while (!done)
> + ? ?usleep (100);
> +
> + ?return NULL;
> +}
> +
> +void *
> +thread_forker (void *arg)
> +{
> + ?int x = * (int *) arg;
> + ?pid_t pid;
> + ?int rv;
> + ?int i;
> + ?pthread_t thread;
> +
> + ?printf ("Thread forker <%d> executing\n", x);
> +
> + ?switch ((pid = fork ()))
> + ? ?{
> + ? ?case -1:
> + ? ? ?assert (0);
> + ? ?default:
> + ? ? ?wait (&rv);
> + ? ? ?done = 1;
> + ? ? ?break;
> + ? ?case 0:
> + ? ? ?i = pthread_create (&thread, NULL, start, NULL);
> + ? ? ?assert (i == 0);
> + ? ? ?i = pthread_join (thread, NULL);
> + ? ? ?assert (i == 0);
> +
> + ? ? ?assert (0);
> + ? ?}
> +
> + ?return NULL;
> +}
> +
> +int
> +main (void)
> +{
> + ?pthread_t threads[NUMTHREADS];
> + ?int args[NUMTHREADS];
> + ?int i, j;
> +
> + ?/* Create a few threads that do mostly nothing, and then one that
> + ? ? forks. ?*/
> + ?for (j = 0; j < NUMTHREADS - 1; ++j)
> + ? ?{
> + ? ? ?args[j] = j;
> + ? ? ?pthread_create (&threads[j], NULL, thread_function, &args[j]);
> + ? ?}
> +
> + ?args[j] = j;
> + ?pthread_create (&threads[j], NULL, thread_forker, &args[j]);
> +
> + ?for (j = 0; j < NUMTHREADS; ++j)
> + ? ?{
> + ? ? ?pthread_join (threads[j], NULL);
> + ? ?}
> +
> + ?return 0;
> +}
> Index: src/gdb/testsuite/gdb.threads/fork-thread-pending.exp
> ===================================================================
> --- /dev/null ? 1970-01-01 00:00:00.000000000 +0000
> +++ src/gdb/testsuite/gdb.threads/fork-thread-pending.exp ? ? ? 2009-05-24 17:29:19.000000000 +0100
> @@ -0,0 +1,128 @@
> +# Copyright (C) 2009 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/>.
> +
> +# There's no support for `set follow-fork-mode' in the remote
> +# protocol.
> +if { [is_remote target] } {
> + ? ?return 0
> +}
> +
> +# Only GNU/Linux is known to support `set follow-fork-mode child'.
> +#
> +if { ! [istarget "*-*-linux*"] } {
> + ? ?return 0
> +}
> +
> +set testfile fork-thread-pending
> +set srcfile ${testfile}.c
> +set binfile ${objdir}/${subdir}/${testfile}
> +
> +if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
> + ? ?return -1
> +}
> +
> +gdb_exit
> +gdb_start
> +gdb_reinitialize_dir $srcdir/$subdir
> +
> +gdb_load ${binfile}
> +if ![runto_main] then {
> + ? fail "Can't run to main"
> + ? return 0
> +}
> +
> +gdb_test "set follow-fork-mode child" "" "1, set follow-fork-mode child"
> +gdb_test "catch fork" "Catchpoint \[0-9\]* \\(fork\\)" "1, insert fork catchpoint"
> +gdb_breakpoint "start" "" "1, set breakpoint at start"
> +
> +gdb_test "continue" "Catchpoint.*" "1, get to the fork event"
> +
> +gdb_test "info threads" " Thread .* Thread .* Thread .* Thread .*" "1, multiple threads found"
> +
> +gdb_test "thread 2" "" "1, switched away from event thread"
> +
> +gdb_test "continue" "Not resuming.*" "1, refused to resume"
> +
> +set test "1, followed to the child, found one thread"
> +gdb_test_multiple "info threads" "metest" {
> + ? ?-re " Thread .* Thread .*$gdb_prompt $" {
> + ? ? ? fail "$test"
> + ? ?}
> + ? ?-re " Thread .*$gdb_prompt $" {
> + ? ? ? pass "$test"
> + ? ?}
> + ? ?-re "$gdb_prompt $" {
> + ? ? ? fail "$test (unknown output)"
> + ? ?}
> + ? ?timeout {
> + ? ? ? fail "$test (timeout)"
> + ? ?}
> +}
> +
> +gdb_test "continue" "Breakpoint 3, start.*" "1, get to the spawned thread in fork child"
> +
> +set test "1, followed to the child, found two threads"
> +gdb_test_multiple "info threads" "$test" {
> + ? ?-re " Thread .* Thread .* Thread .*$gdb_prompt $" {
> + ? ? ? fail "$test"
> + ? ?}
> + ? ?-re " Thread .* Thread .*$gdb_prompt $" {
> + ? ? ? pass "$test"
> + ? ?}
> + ? ?-re "$gdb_prompt $" {
> + ? ? ? fail "$test (unknown output)"
> + ? ?}
> + ? ?timeout {
> + ? ? ? fail "$test (timeout)"
> + ? ?}
> +}
> +
> +# Start over, but this time, don't switch away from the fork event thread.
> +
> +gdb_exit
> +gdb_start
> +gdb_reinitialize_dir $srcdir/$subdir
> +
> +gdb_load ${binfile}
> +if ![runto_main] then {
> + ? fail "Can't run to main"
> + ? return 0
> +}
> +
> +gdb_test "set follow-fork-mode child" "" "2, set follow-fork-mode child"
> +gdb_test "catch fork" "Catchpoint \[0-9\]* \\(fork\\)" "2, insert fork catchpoint"
> +gdb_breakpoint "start"
> +
> +gdb_test "continue" "Catchpoint.*" "2, get to the fork event"
> +
> +gdb_test "info threads" " Thread .* Thread .* Thread .* Thread .*" "2, multiple threads found"
> +
> +gdb_test "continue" "Breakpoint 3, start.*" "2, get to the spawned thread in fork child"
> +
> +set test "2, followed to the child, found two threads"
> +gdb_test_multiple "info threads" "$test" {
> + ? ?-re " Thread .* Thread .* Thread .*$gdb_prompt $" {
> + ? ? ? fail "$test"
> + ? ?}
> + ? ?-re " Thread .* Thread .*$gdb_prompt $" {
> + ? ? ? pass "$test"
> + ? ?}
> + ? ?-re "$gdb_prompt $" {
> + ? ? ? fail "$test (unknown output)"
> + ? ?}
> + ? ?timeout {
> + ? ? ? fail "$test (timeout)"
> + ? ?}
> +}
>

fyi, I just did an update and am getting a build failure (i686-linux).

gcc -m32 -g -O2   -I. -I../../../src/gdb -I../../../src/gdb/common
-I../../../src/gdb/config -DLOCALEDIR="\"/usr/share/locale\""
-DHAVE_CONFIG_H -I../../../src/\
gdb/../include/opcode -I../../../src/gdb/../readline/.. -I../bfd
-I../../../src/gdb/../bfd -I../../../src/gdb/../include
-I../libdecnumber -I../../../src/gdb/..\
/libdecnumber  -I../../../src/gdb/gnulib -Ignulib  -DMI_OUT=1 -DTUI=1
-Wall -Wdeclaration-after-statement -Wpointer-arith
-Wformat-nonliteral -Wno-pointer-sign\
 -Wno-unused -Wno-switch -Wno-char-subscripts -Werror -c -o infrun.o
-MT infrun.o -MMD -MP -MF .deps/infrun.Tpo ../../../src/gdb/infrun.c
cc1: warnings being treated as errors
../../../src/gdb/infrun.c: In function ‘follow_fork’:
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.special_addr_p’
may be used uninitialized in this function
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.code_addr_p’
may be used uninitialized in this function
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.stack_addr_p’
may be used uninitialized in this function
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.special_addr’
may be used uninitialized in this function
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.code_addr’ may
be used uninitialized in this function
../../../src/gdb/infrun.c:298: warning: ‘step_frame_id.stack_addr’ may
be used uninitialized in this function
../../../src/gdb/infrun.c:297: warning: ‘step_range_end’ may be used
uninitialized in this function
../../../src/gdb/infrun.c:296: warning: ‘step_range_start’ may be used
uninitialized in this function
../../../src/gdb/infrun.c:295: warning: ‘step_resume_breakpoint’ may
be used uninitialized in this function
make: *** [infrun.o] Error 1

gcc's not smart enough to detect it's actually ok.

2009-05-24  Doug Evans  <dje@google.com>

        * infrun.c (follow_fork): Initialize new step_* locals
        to avoid "may be used uninitialized" warnings.

Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.377
diff -u -p -r1.377 infrun.c
--- infrun.c    24 May 2009 18:00:08 -0000      1.377
+++ infrun.c    24 May 2009 20:26:28 -0000
@@ -290,12 +290,12 @@ follow_fork (void)

   /* Copy user stepping state to the new inferior thread.  FIXME: the
      followed fork child thread should have a copy of most of the
-     parent thread structure's run control related fields, not just
-     these.  */
-  struct breakpoint *step_resume_breakpoint;
-  CORE_ADDR step_range_start;
-  CORE_ADDR step_range_end;
-  struct frame_id step_frame_id;
+     parent thread structure's run control related fields, not just these.
+     Initialized to avoid "may be used uninitialized" warnings from gcc.  */
+  struct breakpoint *step_resume_breakpoint = NULL;
+  CORE_ADDR step_range_start = 0;
+  CORE_ADDR step_range_end = 0;
+  struct frame_id step_frame_id = { 0 };

   if (!non_stop)
     {