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60adb36c08
A following patch will want to do
string_file str_file;
scoped_restore save_stdout
= make_scoped_restore (&gdb_stdout, &str_file);
where gdb_stdout is a ui_file *, and string_file is a type that
inherits from ui_file, but that doesn't compile today:
src/gdb/top.c: In function ‘std::__cxx11::string execute_command_to_string(char*, int)’:
src/gdb/top.c:710:50: error: no matching function for call to ‘make_scoped_restore(ui_file**, string_file*)’
= make_scoped_restore (&gdb_stdout, &str_file);
^
[...]
In file included from src/gdb/utils.h:25:0,
from src/gdb/defs.h:732,
from src/gdb/top.c:20:
src/gdb/common/scoped_restore.h:94:24: note: candidate: template<class T> scoped_restore_tmpl<T> make_scoped_restore(T*, T)
scoped_restore_tmpl<T> make_scoped_restore (T *var, T value)
^
src/gdb/common/scoped_restore.h:94:24: note: template argument deduction/substitution failed:
src/gdb/top.c:710:50: note: deduced conflicting types for parameter ‘T’ (‘ui_file*’ and ‘string_file*’)
= make_scoped_restore (&gdb_stdout, &str_file);
^
This commit makes code such as the above possible.
gdb/ChangeLog:
2017-01-31 Pedro Alves <palves@redhat.com>
* common/scoped_restore.h
(scoped_restore_tmpl::scoped_restore_tmpl): Template on T2, and
change the value's parameter type to T2.
(make_scoped_restore): Likewise.
103 lines
3.0 KiB
C++
103 lines
3.0 KiB
C++
/* scoped_restore, a simple class for saving and restoring a value
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Copyright (C) 2016-2017 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 SCOPED_RESTORE_H
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#define SCOPED_RESTORE_H
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/* Base class for scoped_restore_tmpl. */
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struct scoped_restore_base
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{
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};
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/* A convenience typedef. Users of make_scoped_restore declare the
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local RAII object as having this type. */
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typedef const scoped_restore_base &scoped_restore;
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/* An RAII-based object that saves a variable's value, and then
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restores it again when this object is destroyed. */
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template<typename T>
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class scoped_restore_tmpl : public scoped_restore_base
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{
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public:
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/* Create a new scoped_restore object that saves the current value
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of *VAR. *VAR will be restored when this scoped_restore object
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is destroyed. */
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scoped_restore_tmpl (T *var)
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: m_saved_var (var),
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m_saved_value (*var)
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{
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}
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/* Create a new scoped_restore object that saves the current value
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of *VAR, and sets *VAR to VALUE. *VAR will be restored when this
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scoped_restore object is destroyed. This is templated on T2 to
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allow passing VALUEs of types convertible to T.
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E.g.: T='base'; T2='derived'. */
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template <typename T2>
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scoped_restore_tmpl (T *var, T2 value)
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: m_saved_var (var),
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m_saved_value (*var)
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{
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*var = value;
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}
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scoped_restore_tmpl (const scoped_restore_tmpl<T> &other)
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: m_saved_var (other.m_saved_var),
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m_saved_value (other.m_saved_value)
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{
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other.m_saved_var = NULL;
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}
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~scoped_restore_tmpl ()
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{
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if (m_saved_var != NULL)
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*m_saved_var = m_saved_value;
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}
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private:
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/* No need for this. It is intentionally not defined anywhere. */
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scoped_restore_tmpl &operator= (const scoped_restore_tmpl &);
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/* The saved variable. */
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mutable T *m_saved_var;
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/* The saved value. */
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const T m_saved_value;
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};
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/* Make a scoped_restore. This is useful because it lets template
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argument deduction work. */
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template<typename T>
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scoped_restore_tmpl<T> make_scoped_restore (T *var)
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{
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return scoped_restore_tmpl<T> (var);
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}
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/* Make a scoped_restore. This is useful because it lets template
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argument deduction work. */
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template<typename T, typename T2>
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scoped_restore_tmpl<T> make_scoped_restore (T *var, T2 value)
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{
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return scoped_restore_tmpl<T> (var, value);
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}
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#endif /* SCOPED_RESTORE_H */
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