binutils-gdb/gdb/infrun.h
Simon Marchi 3ec3145c5d gdb: introduce scoped debug prints
I spent a lot of time reading infrun debug logs recently, and I think
they could be made much more readable by being indented, to clearly see
what operation is done as part of what other operation.  In the current
format, there are no visual cues to tell where things start and end,
it's just a big flat list.  It's also difficult to understand what
caused a given operation (e.g. a call to resume_1) to be done.

To help with this, I propose to add the new scoped_debug_start_end
structure, along with a bunch of macros to make it convenient to use.

The idea of scoped_debug_start_end is simply to print a start and end
message at construction and destruction.  It also increments/decrements
a depth counter in order to make debug statements printed during this
range use some indentation.  Some care is taken to handle the fact that
debug can be turned on or off in the middle of such a range.  For
example, a "set debug foo 1" command in a breakpoint command, or a
superior GDB manually changing the debug_foo variable.

Two macros are added in gdbsupport/common-debug.h, which are helpers to
define module-specific macros:

  - scoped_debug_start_end: takes a message that is printed both at
    construction / destruction, with "start: " and "end: " prefixes.
  - scoped_debug_enter_exit: prints hard-coded "enter" and "exit"
    messages, to denote the entry and exit of a function.

I added some examples in the infrun module to give an idea of how it can
be used and what the result looks like.  The macros are in capital
letters (INFRUN_SCOPED_DEBUG_START_END and
INFRUN_SCOPED_DEBUG_ENTER_EXIT) to mimic the existing SCOPE_EXIT, but
that can be changed if you prefer something else.

Here's an excerpt of the debug
statements printed when doing "continue", where a displaced step is
started:

    [infrun] proceed: enter
      [infrun] proceed: addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT
      [infrun] global_thread_step_over_chain_enqueue: enqueueing thread Thread 0x7ffff75a5640 (LWP 2289301) in global step over chain
      [infrun] start_step_over: enter
        [infrun] start_step_over: stealing global queue of threads to step, length = 1
        [infrun] start_step_over: resuming [Thread 0x7ffff75a5640 (LWP 2289301)] for step-over
        [infrun] resume_1: step=1, signal=GDB_SIGNAL_0, trap_expected=1, current thread [Thread 0x7ffff75a5640 (LWP 2289301)] at 0x5555555551bd
        [displaced] displaced_step_prepare_throw: displaced-stepping Thread 0x7ffff75a5640 (LWP 2289301) now
        [displaced] prepare: selected buffer at 0x5555555550c2
        [displaced] prepare: saved 0x5555555550c2: 1e fa 31 ed 49 89 d1 5e 48 89 e2 48 83 e4 f0 50
        [displaced] amd64_displaced_step_copy_insn: copy 0x5555555551bd->0x5555555550c2: c7 45 fc 00 00 00 00 eb 13 8b 05 d4 2e 00 00 83
        [displaced] displaced_step_prepare_throw: prepared successfully thread=Thread 0x7ffff75a5640 (LWP 2289301), original_pc=0x5555555551bd, displaced_pc=0x5555555550c2
        [displaced] resume_1: run 0x5555555550c2: c7 45 fc 00
        [infrun] infrun_async: enable=1
        [infrun] prepare_to_wait: prepare_to_wait
        [infrun] start_step_over: [Thread 0x7ffff75a5640 (LWP 2289301)] was resumed.
        [infrun] operator(): step-over queue now empty
      [infrun] start_step_over: exit
      [infrun] proceed: start: resuming threads, all-stop-on-top-of-non-stop
        [infrun] proceed: resuming Thread 0x7ffff7da7740 (LWP 2289296)
        [infrun] resume_1: step=0, signal=GDB_SIGNAL_0, trap_expected=0, current thread [Thread 0x7ffff7da7740 (LWP 2289296)] at 0x7ffff7f7d9b7
        [infrun] prepare_to_wait: prepare_to_wait
        [infrun] proceed: resuming Thread 0x7ffff7da6640 (LWP 2289300)
        [infrun] resume_1: thread Thread 0x7ffff7da6640 (LWP 2289300) has pending wait status status->kind = stopped, signal = GDB_SIGNAL_TRAP (currently_stepping=0).
        [infrun] prepare_to_wait: prepare_to_wait
        [infrun] proceed: [Thread 0x7ffff75a5640 (LWP 2289301)] resumed
        [infrun] proceed: resuming Thread 0x7ffff6da4640 (LWP 2289302)
        [infrun] resume_1: thread Thread 0x7ffff6da4640 (LWP 2289302) has pending wait status status->kind = stopped, signal = GDB_SIGNAL_TRAP (currently_stepping=0).
        [infrun] prepare_to_wait: prepare_to_wait
      [infrun] proceed: end: resuming threads, all-stop-on-top-of-non-stop
    [infrun] proceed: exit

We can easily see where the call to `proceed` starts and end.  We can
also see why there are a bunch of resume_1 calls, it's because we are
resuming threads, emulating all-stop on top of a non-stop target.

We also see that debug statements nest well with other modules that have
been migrated to use the "new" debug statement helpers (because they all
use debug_prefixed_vprintf in the end.  I think this is desirable, for
example we could see the debug statements about reading the DWARF info
of a library nested under the debug statements about loading that
library.

Of course, modules that haven't been migrated to use the "new" helpers
will still print without indentations.  This will be one good reason to
migrate them.

I think the runtime cost (when debug statements are disabled) of this is
reasonable, given the improvement in readability.  There is the cost of
the conditionals (like standard debug statements), one more condition
(if (m_must_decrement_print_depth)) and the cost of constructing a stack
object, which means copying a fews pointers.

Adding the print in fetch_inferior_event breaks some tests that use "set
debug infrun", because it prints a debug statement after the prompt.  I
adapted these tests to cope with it, by using the "-prompt" switch of
gdb_test_multiple to as if this debug statement is part of the expected
prompt.  It's unfortunate that we have to do this, but I think the debug
print is useful, and I don't want a few tests to get in the way of
adding good debug output.

gdbsupport/ChangeLog:

	* common-debug.h (debug_print_depth): New.
	(struct scoped_debug_start_end): New.
	(scoped_debug_start_end): New.
	(scoped_debug_enter_exit): New.
	* common-debug.cc (debug_prefixed_vprintf): Print indentation.

gdb/ChangeLog:

	* debug.c (debug_print_depth): New.
	* infrun.h (INFRUN_SCOPED_DEBUG_START_END): New.
	(INFRUN_SCOPED_DEBUG_ENTER_EXIT): New.
	* infrun.c (start_step_over): Use
	INFRUN_SCOPED_DEBUG_ENTER_EXIT.
	(proceed): Use INFRUN_SCOPED_DEBUG_ENTER_EXIT and
	INFRUN_SCOPED_DEBUG_START_END.
	(fetch_inferior_event): Use INFRUN_SCOPED_DEBUG_ENTER_EXIT.

gdbserver/ChangeLog:

	* debug.cc (debug_print_depth): New.

gdb/testsuite/ChangeLog:

        * gdb.base/ui-redirect.exp: Expect infrun debug print after
	prompt.
        * gdb.threads/ia64-sigill.exp: Likewise.
        * gdb.threads/watchthreads-reorder.exp: Likewise.

Change-Id: I7c3805e6487807aa63a1bae318876a0c69dce949
2021-01-04 12:00:54 -05:00

273 lines
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C++

/* Copyright (C) 1986-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef INFRUN_H
#define INFRUN_H 1
#include "symtab.h"
#include "gdbsupport/byte-vector.h"
struct target_waitstatus;
struct frame_info;
struct address_space;
struct return_value_info;
struct process_stratum_target;
struct thread_info;
/* True if we are debugging run control. */
extern bool debug_infrun;
/* Print an "infrun" debug statement. */
#define infrun_debug_printf(fmt, ...) \
debug_prefixed_printf_cond (debug_infrun, "infrun",fmt, ##__VA_ARGS__)
/* Print "infrun" start/end debug statements. */
#define INFRUN_SCOPED_DEBUG_START_END(msg) \
scoped_debug_start_end (debug_infrun, "infrun", msg)
/* Print "infrun" enter/exit debug statements. */
#define INFRUN_SCOPED_DEBUG_ENTER_EXIT \
scoped_debug_enter_exit (debug_infrun, "infrun")
/* Nonzero if we want to give control to the user when we're notified
of shared library events by the dynamic linker. */
extern int stop_on_solib_events;
/* True if execution commands resume all threads of all processes by
default; otherwise, resume only threads of the current inferior
process. */
extern bool sched_multi;
/* 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 bool step_stop_if_no_debug;
/* If set, the inferior should be controlled in non-stop mode. In
this mode, each thread is controlled independently. Execution
commands apply only to the selected thread by default, and stop
events stop only the thread that had the event -- the other threads
are kept running freely. */
extern bool non_stop;
/* When set (default), the target should attempt to disable the
operating system's address space randomization feature when
starting an inferior. */
extern bool disable_randomization;
/* Returns a unique identifier for the current stop. This can be used
to tell whether a command has proceeded the inferior past the
current location. */
extern ULONGEST get_stop_id (void);
/* Reverse execution. */
enum exec_direction_kind
{
EXEC_FORWARD,
EXEC_REVERSE
};
/* The current execution direction. */
extern enum exec_direction_kind execution_direction;
extern void start_remote (int from_tty);
/* Clear out all variables saying what to do when inferior is
continued or stepped. First do this, then set the ones you want,
then call `proceed'. STEP indicates whether we're preparing for a
step/stepi command. */
extern void clear_proceed_status (int step);
extern void proceed (CORE_ADDR, enum gdb_signal);
/* Return a ptid representing the set of threads that we will proceed,
in the perspective of the user/frontend. We may actually resume
fewer threads at first, e.g., if a thread is stopped at a
breakpoint that needs stepping-off, but that should not be visible
to the user/frontend, and neither should the frontend/user be
allowed to proceed any of the threads that happen to be stopped for
internal run control handling, if a previous command wanted them
resumed. */
extern ptid_t user_visible_resume_ptid (int step);
/* Return the process_stratum target that we will proceed, in the
perspective of the user/frontend. If RESUME_PTID is
MINUS_ONE_PTID, then we'll resume all threads of all targets, so
the function returns NULL. Otherwise, we'll be resuming a process
or thread of the current process, so we return the current
inferior's process stratum target. */
extern process_stratum_target *user_visible_resume_target (ptid_t resume_ptid);
/* Return control to GDB when the inferior stops for real. Print
appropriate messages, remove breakpoints, give terminal our modes,
and run the stop hook. Returns true if the stop hook proceeded the
target, false otherwise. */
extern int normal_stop (void);
/* Return the cached copy of the last target/ptid/waitstatus returned
by target_wait()/deprecated_target_wait_hook(). The data is
actually cached by handle_inferior_event(), which gets called
immediately after target_wait()/deprecated_target_wait_hook(). */
extern void get_last_target_status (process_stratum_target **target,
ptid_t *ptid,
struct target_waitstatus *status);
/* Set the cached copy of the last target/ptid/waitstatus. */
extern void set_last_target_status (process_stratum_target *target, ptid_t ptid,
struct target_waitstatus status);
/* Clear the cached copy of the last ptid/waitstatus returned by
target_wait(). */
extern void nullify_last_target_wait_ptid ();
/* Stop all threads. Only returns after everything is halted. */
extern void stop_all_threads (void);
extern void prepare_for_detach (void);
extern void fetch_inferior_event ();
extern void init_wait_for_inferior (void);
extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
struct symtab_and_line ,
struct frame_id);
/* Returns true if we're trying to step past the instruction at
ADDRESS in ASPACE. */
extern int stepping_past_instruction_at (struct address_space *aspace,
CORE_ADDR address);
/* Returns true if thread whose thread number is THREAD is stepping
over a breakpoint. */
extern int thread_is_stepping_over_breakpoint (int thread);
/* Returns true if we're trying to step past an instruction that
triggers a non-steppable watchpoint. */
extern int stepping_past_nonsteppable_watchpoint (void);
/* Record in TP the frame and location we're currently stepping through. */
extern void set_step_info (thread_info *tp,
struct frame_info *frame,
struct symtab_and_line sal);
/* Several print_*_reason helper functions to print why the inferior
has stopped to the passed in UIOUT. */
/* Signal received, print why the inferior has stopped. */
extern void print_signal_received_reason (struct ui_out *uiout,
enum gdb_signal siggnal);
/* Print why the inferior has stopped. We are done with a
step/next/si/ni command, print why the inferior has stopped. */
extern void print_end_stepping_range_reason (struct ui_out *uiout);
/* The inferior was terminated by a signal, print why it stopped. */
extern void print_signal_exited_reason (struct ui_out *uiout,
enum gdb_signal siggnal);
/* The inferior program is finished, print why it stopped. */
extern void print_exited_reason (struct ui_out *uiout, int exitstatus);
/* Reverse execution: target ran out of history info, print why the
inferior has stopped. */
extern void print_no_history_reason (struct ui_out *uiout);
/* Print the result of a function at the end of a 'finish' command.
RV points at an object representing the captured return value/type
and its position in the value history. */
extern void print_return_value (struct ui_out *uiout,
struct return_value_info *rv);
/* Print current location without a level number, if we have changed
functions or hit a breakpoint. Print source line if we have one.
If the execution command captured a return value, print it. If
DISPLAYS is false, do not call 'do_displays'. */
extern void print_stop_event (struct ui_out *uiout, bool displays = true);
/* Pretty print the results of target_wait, for debugging purposes. */
extern void print_target_wait_results (ptid_t waiton_ptid, ptid_t result_ptid,
const struct target_waitstatus *ws);
extern int signal_stop_state (int);
extern int signal_print_state (int);
extern int signal_pass_state (int);
extern int signal_stop_update (int, int);
extern int signal_print_update (int, int);
extern int signal_pass_update (int, int);
extern void update_signals_program_target (void);
/* Clear the convenience variables associated with the exit of the
inferior. Currently, those variables are $_exitcode and
$_exitsignal. */
extern void clear_exit_convenience_vars (void);
/* Dump LEN bytes at BUF in hex to a string and return it. */
extern std::string displaced_step_dump_bytes (const gdb_byte *buf, size_t len);
extern void update_observer_mode (void);
extern void signal_catch_update (const unsigned int *);
/* In some circumstances we allow a command to specify a numeric
signal. The idea is to keep these circumstances limited so that
users (and scripts) develop portable habits. For comparison,
POSIX.2 `kill' requires that 1,2,3,6,9,14, and 15 work (and using a
numeric signal at all is obsolescent. We are slightly more lenient
and allow 1-15 which should match host signal numbers on most
systems. Use of symbolic signal names is strongly encouraged. */
enum gdb_signal gdb_signal_from_command (int num);
/* Enables/disables infrun's async event source in the event loop. */
extern void infrun_async (int enable);
/* Call infrun's event handler the next time through the event
loop. */
extern void mark_infrun_async_event_handler (void);
/* The global chain of threads that need to do a step-over operation
to get past e.g., a breakpoint. */
extern struct thread_info *global_thread_step_over_chain_head;
/* Remove breakpoints if possible (usually that means, if everything
is stopped). On failure, print a message. */
extern void maybe_remove_breakpoints (void);
/* If a UI was in sync execution mode, and now isn't, restore its
prompt (a synchronous execution command has finished, and we're
ready for input). */
extern void all_uis_check_sync_execution_done (void);
/* If a UI was in sync execution mode, and hasn't displayed the prompt
yet, re-disable its prompt (a synchronous execution command was
started or re-started). */
extern void all_uis_on_sync_execution_starting (void);
#endif /* INFRUN_H */