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That is, step past breakpoints by: - pausing all threads - removing breakpoint at PC - single-step - reinsert breakpoint - restart threads similarly to all-stop (with displaced stepping disabled). This allows non-stop to work on targets/architectures without displaced stepping support. That is, it makes displaced stepping an optimization instead of a requirement. For example, in principle, all GNU/Linux ports support non-stop mode at the target_ops level, but not all corresponding gdbarch's implement displaced stepping. This should make non-stop work for all (albeit, not as efficiently). And then there are scenarios where even if the architecture supports displaced stepping, we can't use it, because we e.g., don't find a usable address to use as displaced step scratch pad. It should also fix stepping past watchpoints on targets that have non-continuable watchpoints in non-stop mode (e.g., PPC, untested). Running the instruction out of line in the displaced stepping scratch pad doesn't help that case, as the copied instruction reads/writes the same watched memory... We can fix that too by teaching GDB to only remove the watchpoint from the thread that we want to move past the watchpoint (currently, removing a watchpoint always removes it from all threads), but again, that can be considered an optimization; not all targets would support it. For those familiar with the gdb and gdbserver Linux target_ops backends, the implementation should look similar, except it is done on the core side. When we pause threads, we may find they stop with an interesting event that should be handled later when the thread is re-resumed, thus we store such events in the thread object, and mark the event as pending. We should only consume pending events if the thread is indeed resumed, thus we add a new "resumed" flag to the thread object. At a later stage, we might add new target methods to accelerate some of this, like "pause all threads", with corresponding RSP packets, but we'd still need a fallback method for remote targets that don't support such packets, so, again, that can be deferred as optimization. My _real_ motivation here is making it possible to reimplement all-stop mode on top of the target always working on non-stop mode, so that e.g., we can send RSP packets to a remote target even while the target is running -- can't do that in the all-stop RSP variant, by design). Tested on x86_64 Fedora 20, with and without "set displaced off" forced. The latter forces the new code paths whenever GDB needs to step past a breakpoint. gdb/ChangeLog: 2015-08-07 Pedro Alves <pedro@codesourcery.com> * breakpoint.c (breakpoints_should_be_inserted_now): If any thread has a pending status, return true. * gdbthread.h: Include target/waitstatus.h. (struct thread_suspend_state) <stop_reason, waitstatus_pending_p, stop_pc>: New fields. (struct thread_info) <resumed>: New field. (set_resumed): Declare. * infrun.c: Include "event-loop.h". (infrun_async_inferior_event_token, infrun_is_async): New globals. (infrun_async): New function. (clear_step_over_info): Add debug output. (displaced_step_in_progress_any_inferior): New function. (displaced_step_fixup): New returns int. (start_step_over): Handle in-line step-overs too. Assert the thread is marked resumed. (resume_cleanups): Clear the thread's resumed flag. (resume): Set the thread's resumed flag. Return early if the thread has a pending status. Allow stepping a breakpoint with no signal. (proceed): Adjust to check 'resumed' instead of 'executing'. (clear_proceed_status_thread): If the thread has a pending status, and that status is a finished step, discard the pending status. (clear_proceed_status): Don't clear step_over_info here. (random_pending_event_thread, do_target_wait): New functions. (prepare_for_detach, wait_for_inferior, fetch_inferior_event): Use do_target_wait. (wait_one): New function. (THREAD_STOPPED_BY): New macro. (thread_stopped_by_watchpoint, thread_stopped_by_sw_breakpoint) (thread_stopped_by_hw_breakpoint): New functions. (switch_to_thread_cleanup, save_waitstatus, stop_all_threads): New functions. (handle_inferior_event): Also call set_resumed(false) on all threads implicitly stopped by the event. (restart_threads, resumed_thread_with_pending_status): New functions. (finish_step_over): If we were doing an in-line step-over before, and no longer are after trying to start a new step-over, restart all threads. If we have multiple threads with pending events, save the current event and go through the event loop again. (handle_signal_stop): Return early if finish_step_over returns false. <random signal>: If we get a signal while stepping over a breakpoint in-line in non-stop mode, restart all threads. Clear step_over_info before delivering the signal. (keep_going_stepped_thread): Use internal_error instead of gdb_assert. Mark the thread as resumed. (keep_going_pass_signal): Assert the thread isn't already resumed. If some other thread is doing an in-line step-over, defer the resume. If we just started a new in-line step-over, stop all threads. Don't clear step_over_info. (infrun_async_inferior_event_handler): New function. (_initialize_infrun): Create async event handler with infrun_async_inferior_event_handler as callback. (infrun_async): New declaration. * target.c (target_async): New function. * target.h (target_async): Declare macro and readd as function declaration. * target/waitstatus.h (enum target_stop_reason) <TARGET_STOPPED_BY_SINGLE_STEP>: New value. * thread.c (new_thread): Clear the new waitstatus field. (set_resumed): New function.
199 lines
7.1 KiB
C
199 lines
7.1 KiB
C
/* Copyright (C) 1986-2015 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef INFRUN_H
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#define INFRUN_H 1
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#include "symtab.h"
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struct target_waitstatus;
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struct frame_info;
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struct address_space;
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/* True if we are debugging run control. */
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extern unsigned int debug_infrun;
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/* True if we are debugging displaced stepping. */
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extern int debug_displaced;
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/* Nonzero if we want to give control to the user when we're notified
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of shared library events by the dynamic linker. */
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extern int stop_on_solib_events;
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/* Are we simulating synchronous execution? This is used in async gdb
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to implement the 'run', 'continue' etc commands, which will not
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redisplay the prompt until the execution is actually over. */
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extern int sync_execution;
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/* True if execution commands resume all threads of all processes by
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default; otherwise, resume only threads of the current inferior
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process. */
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extern int sched_multi;
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/* When set, stop the 'step' command if we enter a function which has
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no line number information. The normal behavior is that we step
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over such function. */
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extern int step_stop_if_no_debug;
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/* If set, the inferior should be controlled in non-stop mode. In
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this mode, each thread is controlled independently. Execution
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commands apply only to the selected thread by default, and stop
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events stop only the thread that had the event -- the other threads
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are kept running freely. */
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extern int non_stop;
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/* When set (default), the target should attempt to disable the
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operating system's address space randomization feature when
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starting an inferior. */
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extern int disable_randomization;
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/* Reverse execution. */
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enum exec_direction_kind
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{
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EXEC_FORWARD,
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EXEC_REVERSE
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};
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/* The current execution direction. This should only be set to enum
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exec_direction_kind values. It is only an int to make it
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compatible with make_cleanup_restore_integer. */
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extern int execution_direction;
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extern void start_remote (int from_tty);
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/* Clear out all variables saying what to do when inferior is
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continued or stepped. First do this, then set the ones you want,
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then call `proceed'. STEP indicates whether we're preparing for a
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step/stepi command. */
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extern void clear_proceed_status (int step);
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extern void proceed (CORE_ADDR, enum gdb_signal);
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/* The `resume' routine should only be called in special circumstances.
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Normally, use `proceed', which handles a lot of bookkeeping. */
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extern void resume (enum gdb_signal);
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/* Return a ptid representing the set of threads that we will proceed,
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in the perspective of the user/frontend. We may actually resume
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fewer threads at first, e.g., if a thread is stopped at a
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breakpoint that needs stepping-off, but that should not be visible
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to the user/frontend, and neither should the frontend/user be
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allowed to proceed any of the threads that happen to be stopped for
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internal run control handling, if a previous command wanted them
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resumed. */
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extern ptid_t user_visible_resume_ptid (int step);
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extern void wait_for_inferior (void);
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extern void normal_stop (void);
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extern void get_last_target_status (ptid_t *ptid,
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struct target_waitstatus *status);
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extern void prepare_for_detach (void);
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extern void fetch_inferior_event (void *);
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extern void init_wait_for_inferior (void);
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extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
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struct symtab_and_line ,
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struct frame_id);
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/* Returns true if we're trying to step past the instruction at
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ADDRESS in ASPACE. */
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extern int stepping_past_instruction_at (struct address_space *aspace,
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CORE_ADDR address);
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/* Returns true if we're trying to step past an instruction that
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triggers a non-steppable watchpoint. */
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extern int stepping_past_nonsteppable_watchpoint (void);
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extern void set_step_info (struct frame_info *frame,
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struct symtab_and_line sal);
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/* Several print_*_reason helper functions to print why the inferior
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has stopped to the passed in UIOUT. */
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/* Signal received, print why the inferior has stopped. */
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extern void print_signal_received_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* Print why the inferior has stopped. We are done with a
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step/next/si/ni command, print why the inferior has stopped. */
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extern void print_end_stepping_range_reason (struct ui_out *uiout);
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/* The inferior was terminated by a signal, print why it stopped. */
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extern void print_signal_exited_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* The inferior program is finished, print why it stopped. */
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extern void print_exited_reason (struct ui_out *uiout, int exitstatus);
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/* Reverse execution: target ran out of history info, print why the
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inferior has stopped. */
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extern void print_no_history_reason (struct ui_out *uiout);
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extern void print_stop_event (struct target_waitstatus *ws);
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extern int signal_stop_state (int);
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extern int signal_print_state (int);
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extern int signal_pass_state (int);
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extern int signal_stop_update (int, int);
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extern int signal_print_update (int, int);
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extern int signal_pass_update (int, int);
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extern void update_signals_program_target (void);
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/* Clear the convenience variables associated with the exit of the
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inferior. Currently, those variables are $_exitcode and
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$_exitsignal. */
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extern void clear_exit_convenience_vars (void);
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/* Dump LEN bytes at BUF in hex to FILE, followed by a newline. */
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extern void displaced_step_dump_bytes (struct ui_file *file,
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const gdb_byte *buf, size_t len);
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extern struct displaced_step_closure *get_displaced_step_closure_by_addr
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(CORE_ADDR addr);
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extern void update_observer_mode (void);
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extern void signal_catch_update (const unsigned int *);
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/* In some circumstances we allow a command to specify a numeric
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signal. The idea is to keep these circumstances limited so that
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users (and scripts) develop portable habits. For comparison,
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POSIX.2 `kill' requires that 1,2,3,6,9,14, and 15 work (and using a
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numeric signal at all is obsolescent. We are slightly more lenient
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and allow 1-15 which should match host signal numbers on most
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systems. Use of symbolic signal names is strongly encouraged. */
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enum gdb_signal gdb_signal_from_command (int num);
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/* Enables/disables infrun's async event source in the event loop. */
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extern void infrun_async (int enable);
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/* The global queue of threads that need to do a step-over operation
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to get past e.g., a breakpoint. */
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extern struct thread_info *step_over_queue_head;
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#endif /* INFRUN_H */
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