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binutils-gdb/gdb/observable.h
Simon Marchi 8480a37e14 gdb: pass frames as const frame_info_ptr & 
We currently pass frames to function by value, as `frame_info_ptr`.
This is somewhat expensive:

 - the size of `frame_info_ptr` is 64 bytes, which is a bit big to pass
   by value
 - the constructors and destructor link/unlink the object in the global
   `frame_info_ptr::frame_list` list.  This is an `intrusive_list`, so
   it's not so bad: it's just assigning a few points, there's no memory
   allocation as if it was `std::list`, but still it's useless to do
   that over and over.

As suggested by Tom Tromey, change many function signatures to accept
`const frame_info_ptr &` instead of `frame_info_ptr`.

Some functions reassign their `frame_info_ptr` parameter, like:

  void
  the_func (frame_info_ptr frame)
  {
    for (; frame != nullptr; frame = get_prev_frame (frame))
      {
        ...
      }
  }

I wondered what to do about them, do I leave them as-is or change them
(and need to introduce a separate local variable that can be
re-assigned).  I opted for the later for consistency.  It might not be
clear why some functions take `const frame_info_ptr &` while others take
`frame_info_ptr`.  Also, if a function took a `frame_info_ptr` because
it did re-assign its parameter, I doubt that we would think to change it
to `const frame_info_ptr &` should the implementation change such that
it doesn't need to take `frame_info_ptr` anymore.  It seems better to
have a simple rule and apply it everywhere.

Change-Id: I59d10addef687d157f82ccf4d54f5dde9a963fd0
Approved-By: Andrew Burgess <aburgess@redhat.com>
2024-02-20 10:42:25 -05:00

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/* Observers
Copyright (C) 2016-2024 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 OBSERVABLE_H
#define OBSERVABLE_H
#include "gdbsupport/observable.h"
#include "target/waitstatus.h"
struct bpstat;
struct solib;
struct objfile;
struct thread_info;
struct inferior;
struct process_stratum_target;
struct target_ops;
struct trace_state_variable;
struct program_space;
namespace gdb
{
namespace observers
{
/* The inferior has stopped for real. The BS argument describes the
breakpoints were are stopped at, if any. Second argument
PRINT_FRAME non-zero means display the location where the
inferior has stopped.
gdb notifies all normal_stop observers when the inferior execution
has just stopped, the associated messages and annotations have been
printed, and the control is about to be returned to the user.
Note that the normal_stop notification is not emitted when the
execution stops due to a breakpoint, and this breakpoint has a
condition that is not met. If the breakpoint has any associated
commands list, the commands are executed after the notification is
emitted. */
extern observable<struct bpstat */* bs */, int /* print_frame */> normal_stop;
/* The inferior was stopped by a signal. */
extern observable<enum gdb_signal /* siggnal */> signal_received;
/* The target's register contents have changed. */
extern observable<struct target_ops */* target */> target_changed;
/* The executable being debugged by GDB in PSPACE has changed: The user
decided to debug a different program, or the program he was debugging
has been modified since being loaded by the debugger (by being
recompiled, for instance). The path to the new executable can be found
by examining PSPACE->exec_filename.
When RELOAD is true the path to the executable hasn't changed, but the
file does appear to have changed, so GDB reloaded it, e.g. if the user
recompiled the executable. when RELOAD is false then the path to the
executable has not changed. */
extern observable<struct program_space */* pspace */,
bool /*reload */> executable_changed;
/* gdb has just connected to an inferior. For 'run', gdb calls this
observer while the inferior is still stopped at the entry-point
instruction. For 'attach' and 'core', gdb calls this observer
immediately after connecting to the inferior, and before any
information on the inferior has been printed. */
extern observable<inferior */* inferior */> inferior_created;
/* The inferior EXEC_INF has exec'ed a new executable file.
Execution continues in FOLLOW_INF, which may or may not be the same as
EXEC_INF, depending on "set follow-exec-mode". */
extern observable<inferior */* exec_inf */, inferior */* follow_inf */>
inferior_execd;
/* The inferior PARENT_INF has forked. If we are setting up an inferior for
the child (because we follow only the child or we follow both), CHILD_INF
is the child inferior. Otherwise, CHILD_INF is nullptr.
FORK_KIND is TARGET_WAITKIND_FORKED or TARGET_WAITKIND_VFORKED. */
extern observable<inferior */* parent_inf */, inferior */* child_inf */,
target_waitkind /* fork_kind */> inferior_forked;
/* The shared library specified by SOLIB has been loaded. Note that
when gdb calls this observer, the library's symbols probably
haven't been loaded yet. */
extern observable<solib &/* solib */> solib_loaded;
/* The shared library SOLIB has been unloaded from program space PSPACE.
Note when gdb calls this observer, the library's symbols have not
been unloaded yet, and thus are still available. */
extern observable<program_space *, const solib &/* solib */> solib_unloaded;
/* The symbol file specified by OBJFILE has been loaded. */
extern observable<struct objfile */* objfile */> new_objfile;
/* All objfiles from PSPACE were removed. */
extern observable<program_space */* pspace */> all_objfiles_removed;
/* The object file specified by OBJFILE is about to be freed. */
extern observable<struct objfile */* objfile */> free_objfile;
/* The thread specified by T has been created. */
extern observable<struct thread_info */* t */> new_thread;
/* The thread specified by T has exited. EXIT_CODE is the thread's
exit code, if available. The SILENT argument indicates that GDB is
removing the thread from its tables without wanting to notify the
CLI about it. */
extern observable<thread_info */* t */,
std::optional<ULONGEST> /* exit_code */,
bool /* silent */> thread_exit;
/* The thread specified by T has been deleted, with delete_thread.
This is called just before the thread_info object is destroyed with
operator delete. */
extern observable<thread_info */* t */> thread_deleted;
/* An explicit stop request was issued to PTID. If PTID equals
minus_one_ptid, the request applied to all threads. If
ptid_is_pid(PTID) returns true, the request applied to all
threads of the process pointed at by PTID. Otherwise, the
request applied to the single thread pointed at by PTID. */
extern observable<ptid_t /* ptid */> thread_stop_requested;
/* The target was resumed. The PTID parameter specifies which
thread was resume, and may be RESUME_ALL if all threads are
resumed. */
extern observable<ptid_t /* ptid */> target_resumed;
/* The target is about to be proceeded. */
extern observable<> about_to_proceed;
/* A new breakpoint B has been created. */
extern observable<struct breakpoint */* b */> breakpoint_created;
/* A breakpoint has been destroyed. The argument B is the
pointer to the destroyed breakpoint. */
extern observable<struct breakpoint */* b */> breakpoint_deleted;
/* A breakpoint has been modified in some way. The argument B
is the modified breakpoint. */
extern observable<struct breakpoint */* b */> breakpoint_modified;
/* GDB has instantiated a new architecture, NEWARCH is a pointer to the new
architecture. */
extern observable<struct gdbarch */* newarch */> new_architecture;
/* The thread's ptid has changed. The OLD_PTID parameter specifies
the old value, and NEW_PTID specifies the new value. */
extern observable<process_stratum_target * /* target */,
ptid_t /* old_ptid */, ptid_t /* new_ptid */>
thread_ptid_changed;
/* The inferior INF has been added to the list of inferiors. At
this point, it might not be associated with any process. */
extern observable<struct inferior */* inf */> inferior_added;
/* The inferior identified by INF has been attached to a
process. */
extern observable<struct inferior */* inf */> inferior_appeared;
/* Inferior INF is about to be detached. */
extern observable<struct inferior */* inf */> inferior_pre_detach;
/* Either the inferior associated with INF has been detached from
the process, or the process has exited. */
extern observable<struct inferior */* inf */> inferior_exit;
/* The inferior INF has been removed from the list of inferiors.
This method is called immediately before freeing INF. */
extern observable<struct inferior */* inf */> inferior_removed;
/* The inferior CLONE has been created by cloning INF. */
extern observable<struct inferior */* inf */, struct inferior */* clone */>
inferior_cloned;
/* Bytes from DATA to DATA + LEN have been written to the inferior
at ADDR. */
extern observable<struct inferior */* inferior */, CORE_ADDR /* addr */,
ssize_t /* len */, const bfd_byte */* data */>
memory_changed;
/* Called before a top-level prompt is displayed. CURRENT_PROMPT is
the current top-level prompt. */
extern observable<const char */* current_prompt */> before_prompt;
/* Variable gdb_datadir has been set. The value may not necessarily
change. */
extern observable<> gdb_datadir_changed;
/* An inferior function at ADDRESS is about to be called in thread
THREAD. */
extern observable<ptid_t /* thread */, CORE_ADDR /* address */>
inferior_call_pre;
/* The inferior function at ADDRESS has just been called. This
observer is called even if the inferior exits during the call.
THREAD is the thread in which the function was called, which may
be different from the current thread. */
extern observable<ptid_t /* thread */, CORE_ADDR /* address */>
inferior_call_post;
/* A register in the inferior has been modified by the gdb user. */
extern observable<const frame_info_ptr &/* frame */, int /* regnum */>
register_changed;
/* The user-selected inferior, thread and/or frame has changed. The
user_select_what flag specifies if the inferior, thread and/or
frame has changed. */
extern observable<user_selected_what /* selection */>
user_selected_context_changed;
/* This is notified when a styling setting has changed, content may need
to be updated based on the new settings. */
extern observable<> styling_changed;
/* The CLI's notion of the current source has changed. This differs
from user_selected_context_changed in that it is also set by the
"list" command. */
extern observable<> current_source_symtab_and_line_changed;
/* Called when GDB is about to exit. */
extern observable<int> gdb_exiting;
/* When a connection is removed. */
extern observable<process_stratum_target */* target */> connection_removed;
/* About to enter target_wait (). */
extern observable <ptid_t /* ptid */> target_pre_wait;
/* About to leave target_wait (). */
extern observable <ptid_t /* event_ptid */> target_post_wait;
/* New program space PSPACE was created. */
extern observable <program_space */* pspace */> new_program_space;
/* The program space PSPACE is about to be deleted. */
extern observable <program_space */* pspace */> free_program_space;
} /* namespace observers */
} /* namespace gdb */
#endif /* OBSERVABLE_H */
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