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f8631e5e04
[I sent this earlier today, but I don't see it in the archives.
Resending it through a different computer / SMTP.]
The use of the static buffer in command_line_input is becoming
problematic, as explained here [1]. In short, with this patch [2] that
attempt to fix a post-hook bug, when running gdb.base/commands.exp, we
hit a case where we read a "define" command line from a script file
using command_command_line_input. The command line is stored in
command_line_input's static buffer. Inside the define command's
execution, we read the lines inside the define using command_line_input,
which overwrites the define command, in command_line_input's static
buffer. After the execution of the define command, execute_command does
a command look up to see if a post-hook is registered. For that, it
uses a now stale pointer that used to point to the define command, in
the static buffer, causing a use-after-free. Note that the pointer in
execute_command points to the dynamically-allocated buffer help by the
static buffer in command_line_input, not to the static object itself,
hence why we see a use-after-free.
Fix that by removing the static buffer. I initially changed
command_line_input and other related functions to return an std::string,
which is the obvious but naive solution. The thing is that some callees
don't need to return an allocated string, so this this an unnecessary
pessimization. I changed it to passing in a reference to an std::string
buffer, which the callee can use if it needs to return
dynamically-allocated content. It fills the buffer and returns a
pointers to the C string inside. The callees that don't need to return
dynamically-allocated content simply don't use it.
So, it started with modifying command_line_input as described above, all
the other changes derive directly from that.
One slightly shady thing is in handle_line_of_input, where we now pass a
pointer to an std::string's internal buffer to readline's history_value
function, which takes a `char *`. I'm pretty sure that this function
does not modify the input string, because I was able to change it (with
enough massaging) to take a `const char *`.
A subtle change is that we now clear a UI's line buffer using a
SCOPE_EXIT in command_line_handler, after executing the command.
This was previously done by this line in handle_line_of_input:
/* We have a complete command line now. Prepare for the next
command, but leave ownership of memory to the buffer . */
cmd_line_buffer->used_size = 0;
I think the new way is clearer.
[1] https://inbox.sourceware.org/gdb-patches/becb8438-81ef-8ad8-cc42-fcbfaea8cddd@simark.ca/
[2] https://inbox.sourceware.org/gdb-patches/20221213112241.621889-1-jan.vrany@labware.com/
Change-Id: I8fc89b1c69870c7fc7ad9c1705724bd493596300
Reviewed-By: Tom Tromey <tom@tromey.com>
302 lines
9.5 KiB
C++
302 lines
9.5 KiB
C++
/* Top level stuff for GDB, the GNU debugger.
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Copyright (C) 1986-2022 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 TOP_H
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#define TOP_H
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#include "gdbsupport/buffer.h"
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#include "gdbsupport/event-loop.h"
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#include "gdbsupport/next-iterator.h"
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#include "value.h"
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/* Prompt state. */
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enum prompt_state
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{
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/* The command line is blocked simulating synchronous execution.
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This is used to implement the foreground execution commands
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('run', 'continue', etc.). We won't display the prompt and
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accept further commands until the execution is actually over. */
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PROMPT_BLOCKED,
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/* The command finished; display the prompt before returning back to
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the top level. */
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PROMPT_NEEDED,
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/* We've displayed the prompt already, ready for input. */
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PROMPTED,
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};
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/* All about a user interface instance. Each user interface has its
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own I/O files/streams, readline state, its own top level
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interpreter (for the main UI, this is the interpreter specified
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with -i on the command line) and secondary interpreters (for
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interpreter-exec ...), etc. There's always one UI associated with
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stdin/stdout/stderr, but the user can create secondary UIs, for
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example, to create a separate MI channel on its own stdio
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streams. */
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struct ui
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{
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/* Create a new UI. */
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ui (FILE *instream, FILE *outstream, FILE *errstream);
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~ui ();
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DISABLE_COPY_AND_ASSIGN (ui);
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/* Pointer to next in singly-linked list. */
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struct ui *next = nullptr;
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/* Convenient handle (UI number). Unique across all UIs. */
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int num;
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/* The UI's command line buffer. This is to used to accumulate
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input until we have a whole command line. */
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std::string line_buffer;
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/* The callback used by the event loop whenever an event is detected
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on the UI's input file descriptor. This function incrementally
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builds a buffer where it accumulates the line read up to the
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point of invocation. In the special case in which the character
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read is newline, the function invokes the INPUT_HANDLER callback
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(see below). */
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void (*call_readline) (gdb_client_data) = nullptr;
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/* The function to invoke when a complete line of input is ready for
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processing. */
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void (*input_handler) (gdb::unique_xmalloc_ptr<char> &&) = nullptr;
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/* True if this UI is using the readline library for command
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editing; false if using GDB's own simple readline emulation, with
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no editing support. */
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int command_editing = 0;
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/* Each UI has its own independent set of interpreters. */
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struct ui_interp_info *interp_info = nullptr;
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/* True if the UI is in async mode, false if in sync mode. If in
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sync mode, a synchronous execution command (e.g, "next") does not
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return until the command is finished. If in async mode, then
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running a synchronous command returns right after resuming the
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target. Waiting for the command's completion is later done on
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the top event loop. For the main UI, this starts out disabled,
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until all the explicit command line arguments (e.g., `gdb -ex
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"start" -ex "next"') are processed. */
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int async = 0;
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/* The number of nested readline secondary prompts that are
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currently active. */
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int secondary_prompt_depth = 0;
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/* The UI's stdin. Set to stdin for the main UI. */
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FILE *stdin_stream;
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/* stdio stream that command input is being read from. Set to stdin
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normally. Set by source_command to the file we are sourcing.
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Set to NULL if we are executing a user-defined command or
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interacting via a GUI. */
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FILE *instream;
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/* Standard output stream. */
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FILE *outstream;
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/* Standard error stream. */
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FILE *errstream;
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/* The file descriptor for the input stream, so that we can register
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it with the event loop. This can be set to -1 to prevent this
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registration. */
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int input_fd;
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/* Whether ISATTY returns true on input_fd. Cached here because
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quit_force needs to know this _after_ input_fd might be
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closed. */
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bool m_input_interactive_p;
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/* See enum prompt_state's description. */
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enum prompt_state prompt_state = PROMPT_NEEDED;
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/* The fields below that start with "m_" are "private". They're
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meant to be accessed through wrapper macros that make them look
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like globals. */
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/* The ui_file streams. */
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/* Normal results */
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struct ui_file *m_gdb_stdout;
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/* Input stream */
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struct ui_file *m_gdb_stdin;
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/* Serious error notifications */
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struct ui_file *m_gdb_stderr;
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/* Log/debug/trace messages that should bypass normal stdout/stderr
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filtering. */
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struct ui_file *m_gdb_stdlog;
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/* The current ui_out. */
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struct ui_out *m_current_uiout = nullptr;
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/* Register the UI's input file descriptor in the event loop. */
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void register_file_handler ();
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/* Unregister the UI's input file descriptor from the event loop. */
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void unregister_file_handler ();
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/* Return true if this UI's input fd is a tty. */
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bool input_interactive_p () const;
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};
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/* The main UI. This is the UI that is bound to stdin/stdout/stderr.
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It always exists and is created automatically when GDB starts
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up. */
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extern struct ui *main_ui;
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/* The current UI. */
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extern struct ui *current_ui;
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/* The list of all UIs. */
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extern struct ui *ui_list;
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/* State for SWITCH_THRU_ALL_UIS. */
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class switch_thru_all_uis
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{
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public:
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switch_thru_all_uis () : m_iter (ui_list), m_save_ui (¤t_ui)
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{
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current_ui = ui_list;
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}
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DISABLE_COPY_AND_ASSIGN (switch_thru_all_uis);
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/* If done iterating, return true; otherwise return false. */
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bool done () const
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{
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return m_iter == NULL;
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}
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/* Move to the next UI, setting current_ui if iteration is not yet
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complete. */
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void next ()
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{
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m_iter = m_iter->next;
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if (m_iter != NULL)
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current_ui = m_iter;
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}
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private:
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/* Used to iterate through the UIs. */
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struct ui *m_iter;
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/* Save and restore current_ui. */
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scoped_restore_tmpl<struct ui *> m_save_ui;
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};
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/* Traverse through all UI, and switch the current UI to the one
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being iterated. */
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#define SWITCH_THRU_ALL_UIS() \
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for (switch_thru_all_uis stau_state; !stau_state.done (); stau_state.next ())
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using ui_range = next_range<ui>;
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/* An adapter that can be used to traverse over all UIs. */
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static inline
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ui_range all_uis ()
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{
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return ui_range (ui_list);
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}
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/* From top.c. */
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extern bool confirm;
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extern int inhibit_gdbinit;
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/* Print the GDB version banner to STREAM. If INTERACTIVE is false,
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then information referring to commands (e.g., "show configuration")
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is omitted; this mode is used for the --version command line
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option. If INTERACTIVE is true, then interactive commands are
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mentioned. */
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extern void print_gdb_version (struct ui_file *stream, bool interactive);
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extern void print_gdb_configuration (struct ui_file *);
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extern void read_command_file (FILE *);
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extern void init_history (void);
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extern void command_loop (void);
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extern int quit_confirm (void);
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extern void quit_force (int *, int);
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extern void quit_command (const char *, int);
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extern void quit_cover (void);
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extern void execute_command (const char *, int);
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/* If the interpreter is in sync mode (we're running a user command's
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list, running command hooks or similars), and we just ran a
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synchronous command that started the target, wait for that command
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to end. WAS_SYNC indicates whether sync_execution was set before
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the command was run. */
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extern void maybe_wait_sync_command_done (int was_sync);
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/* Wait for a synchronous execution command to end. */
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extern void wait_sync_command_done (void);
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extern void check_frame_language_change (void);
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/* Prepare for execution of a command.
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Call this before every command, CLI or MI.
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Returns a cleanup to be run after the command is completed. */
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extern scoped_value_mark prepare_execute_command (void);
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/* This function returns a pointer to the string that is used
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by gdb for its command prompt. */
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extern const std::string &get_prompt ();
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/* This function returns a pointer to the string that is used
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by gdb for its command prompt. */
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extern void set_prompt (const char *s);
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/* Return 1 if UI's current input handler is a secondary prompt, 0
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otherwise. */
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extern int gdb_in_secondary_prompt_p (struct ui *ui);
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/* Perform _initialize initialization. */
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extern void gdb_init ();
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/* For use by event-top.c. */
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/* Variables from top.c. */
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extern int source_line_number;
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extern std::string source_file_name;
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extern bool history_expansion_p;
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extern bool server_command;
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extern char *lim_at_start;
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extern void gdb_add_history (const char *);
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extern void show_commands (const char *args, int from_tty);
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extern void set_verbose (const char *, int, struct cmd_list_element *);
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extern const char *handle_line_of_input (std::string &cmd_line_buffer,
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const char *rl, int repeat,
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const char *annotation_suffix);
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/* Call at startup to see if the user has requested that gdb start up
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quietly. */
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extern bool check_quiet_mode ();
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#endif
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