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200fd2874d
While working on a later patch that required me to understand how GDB
starts up inferiors, I was confused by the
target_ops::post_startup_inferior method.
The post_startup_inferior target function is only called from
inf_ptrace_target::create_inferior.
Part of the target class hierarchy looks like this:
inf_child_target
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'-- inf_ptrace_target
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|-- linux_nat_target
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|-- fbsd_nat_target
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|-- nbsd_nat_target
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|-- obsd_nat_target
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'-- rs6000_nat_target
Every sub-class of inf_ptrace_target, except rs6000_nat_target,
implements ::post_startup_inferior. The rs6000_nat_target picks up
the implementation of ::post_startup_inferior not from
inf_ptrace_target, but from inf_child_target.
No descendent of inf_child_target, outside the inf_ptrace_target
sub-tree, implements ::post_startup_inferior, which isn't really
surprising, as they would never see the method called (remember, the
method is only called from inf_ptrace_target::create_inferior).
What I find confusing is the role inf_child_target plays in
implementing, what is really a helper function for just one of its
descendents.
In this commit I propose that we formally make ::post_startup_inferior
a helper function of inf_ptrace_target. To do this I will remove the
::post_startup_inferior from the target_ops API, and instead make this
a protected, pure virtual function on inf_ptrace_target.
I'll remove the empty implementation of ::post_startup_inferior from
the inf_child_target class, and add a new empty implementation to the
rs6000_nat_target class.
All the other descendents of inf_ptrace_target already provide an
implementation of this method and so don't need to change beyond
making the method protected within their class declarations.
To me, this makes much more sense now. The helper function, which is
only called from within the inf_ptrace_target class, is now a part of
the inf_ptrace_target class.
The only way in which this change is visible to a user is if the user
turns on 'set debug target 1'. With this debug flag on, prior to this
patch the user would see something like:
-> native->post_startup_inferior (...)
<- native->post_startup_inferior (2588939)
After this patch these lines are no longer present, as the
post_startup_inferior is no longer a top level target method. For me,
this is an acceptable change.
119 lines
4.0 KiB
C++
119 lines
4.0 KiB
C++
/* Base/prototype target for default child (native) targets.
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Copyright (C) 2004-2021 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 INF_CHILD_H
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#define INF_CHILD_H
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#include "target.h"
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#include "process-stratum-target.h"
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/* A prototype child target. The client can override it with local
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methods. */
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class inf_child_target
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: public memory_breakpoint_target<process_stratum_target>
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{
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public:
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inf_child_target () = default;
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~inf_child_target () override = 0;
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const target_info &info () const override;
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void close () override;
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void disconnect (const char *, int) override;
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void fetch_registers (struct regcache *, int) override = 0;
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void store_registers (struct regcache *, int) override = 0;
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void prepare_to_store (struct regcache *) override;
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bool supports_terminal_ours () override;
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void terminal_init () override;
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void terminal_inferior () override;
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void terminal_save_inferior () override;
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void terminal_ours_for_output () override;
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void terminal_ours () override;
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void terminal_info (const char *, int) override;
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void interrupt () override;
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void pass_ctrlc () override;
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void follow_exec (inferior *follow_inf, ptid_t ptid,
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const char *execd_pathname) override;
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void mourn_inferior () override;
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bool can_run () override;
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bool can_create_inferior () override;
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void create_inferior (const char *, const std::string &,
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char **, int) override = 0;
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bool can_attach () override;
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void attach (const char *, int) override = 0;
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void post_attach (int) override;
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char *pid_to_exec_file (int pid) override;
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int fileio_open (struct inferior *inf, const char *filename,
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int flags, int mode, int warn_if_slow,
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int *target_errno) override;
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int fileio_pwrite (int fd, const gdb_byte *write_buf, int len,
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ULONGEST offset, int *target_errno) override;
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int fileio_pread (int fd, gdb_byte *read_buf, int len,
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ULONGEST offset, int *target_errno) override;
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int fileio_fstat (int fd, struct stat *sb, int *target_errno) override;
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int fileio_close (int fd, int *target_errno) override;
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int fileio_unlink (struct inferior *inf,
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const char *filename,
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int *target_errno) override;
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gdb::optional<std::string> fileio_readlink (struct inferior *inf,
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const char *filename,
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int *target_errno) override;
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bool use_agent (bool use) override;
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bool can_use_agent () override;
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protected:
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/* Unpush the target if it wasn't explicitly open with "target native"
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and there are no live inferiors left. Note: if calling this as a
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result of a mourn or detach, the current inferior shall already
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have its PID cleared, so it isn't counted as live. That's usually
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done by calling either generic_mourn_inferior or
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detach_inferior. */
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void maybe_unpush_target ();
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};
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/* Convert the host wait(2) status to a target_waitstatus. */
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extern target_waitstatus host_status_to_waitstatus (int hoststatus);
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/* Register TARGET as native target and set it up to respond to the
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"target native" command. */
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extern void add_inf_child_target (inf_child_target *target);
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/* target_open_ftype callback for inf-child targets. Used by targets
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that want to register an alternative target_info object. Most
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targets use add_inf_child_target instead. */
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extern void inf_child_open_target (const char *arg, int from_tty);
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#endif
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