69 lines
2.2 KiB
C
69 lines
2.2 KiB
C
|
/************************************************************************
|
||
|
|
**
|
||
|
|
** @file lambdaconstants.h
|
||
|
|
** @author Roman Telezhynskyi <dismine(at)gmail.com>
|
||
|
|
** @date 29 1, 2022
|
||
|
|
**
|
||
|
|
** @brief
|
||
|
|
** @copyright
|
||
|
|
** This source code is part of the Valentina project, a pattern making
|
||
|
|
** program, whose allow create and modeling patterns of clothing.
|
||
|
|
** Copyright (C) 2022 Valentina project
|
||
|
|
** <https://gitlab.com/smart-pattern/valentina> All Rights Reserved.
|
||
|
|
**
|
||
|
|
** Valentina 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.
|
||
|
|
**
|
||
|
|
** Valentina 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 Valentina. If not, see <http://www.gnu.org/licenses/>.
|
||
|
|
**
|
||
|
|
*************************************************************************/
|
||
|
|
#ifndef LAMBDACONSTANTS_H
|
||
|
|
#define LAMBDACONSTANTS_H
|
||
|
|
|
||
|
|
/*
|
||
|
|
given a lambda that wants to capture two constants
|
||
|
|
|
||
|
|
const auto k1 = 1000;
|
||
|
|
const auto k2 = 2000;
|
||
|
|
int v = 0;
|
||
|
|
|
||
|
|
auto lambda = [&v, &k1, &k2]() {
|
||
|
|
v = k1 * k2;
|
||
|
|
}
|
||
|
|
|
||
|
|
Then unfortunately clang will correctly warn about unnecessary captures. And MSVC will fail to compile if you don't
|
||
|
|
capture.
|
||
|
|
|
||
|
|
https://stackoverflow.com/questions/52416362/unused-lambda-capture-warning-when-capture-is-actually-used
|
||
|
|
|
||
|
|
An imperfect solution is to declare the lambda using the V_LAMBDA_CONSTANTS macro.
|
||
|
|
|
||
|
|
auto lambda = [&v
|
||
|
|
V_LAMBDA_CONSTANTS(&k1, &k2)
|
||
|
|
](){
|
||
|
|
v = k1 * k2;
|
||
|
|
}
|
||
|
|
|
||
|
|
This should work correctly. Most of the time.
|
||
|
|
|
||
|
|
NOTE: There is no comma after the final capture variable before the V_LAMBDA_CONSTANTS macro. The macro is variadic and
|
||
|
|
will work with 1 or more captures.
|
||
|
|
*/
|
||
|
|
#ifndef V_LAMBDA_CONSTANTS
|
||
|
|
#if defined(Q_CC_MSVC)
|
||
|
|
#define V_LAMBDA_CONSTANTS(...) ,__VA_ARGS__
|
||
|
|
#else
|
||
|
|
#define V_LAMBDA_CONSTANTS(...)
|
||
|
|
#endif
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif // LAMBDACONSTANTS_H
|