我最近将 gcc 和 g++ 更新到了 7.2 版。我想特别尝试 std::experimental::any 和 std::variant，我在 QtCreator 中使用 Qt 5.9.1。
到目前为止，我已经在项目文件中写了这个:
CONFIG += c++17
我已经在正确的地方添加了正确的标题:
#include <variant>
#include <experimental/any>
任何工作都很好，没有问题。但是，当我包含变体头文件时，我收到此错误:
/usr/include/c++/7/bits/c++17_warning.h:32: error: #error This file requires compiler and library support for the ISO C++ 2017 standard. This support must be enabled with the -std=c++17 or -std=gnu++17 compiler options.
#error 此文件需要编译器和库支持\ ^~~~~
我在项目文件中尝试了很多东西，这里是完整列表:
CONFIG += c++17
&
CONFIG += c++1z
&
QMAKE_CXXFLAGS += -std=c++17
&
QMAKE_CXXFLAGS += -std=c++1z
&
CONFIG += c++17
QMAKE_CXXFLAGS += -std=c++17
&
CONFIG += c++1z
QMAKE_CXXFLAGS += -std=c++1z
&
CONFIG += c++11
CONFIG += c++14
CONFIG += c++17
这是我能想到的所有黑暗中的刺伤。我错过了什么？为什么 experimental::any 编译而变体不编译？
我知道我不应该以这种方式将 CONFIG += c++xx 和 QMAKE_CXXFLAGS 一起使用，但我想我还是试试吧其他作品。对于奖励积分，我还想知道，当我已经配置 17 时，是否应该添加 14 和 11 的配置调用？
编辑:
这是我的大部分文件名被清除的编译器输出:
18:04:10: Running steps for project AIQt...
18:04:10: Configuration unchanged, skipping qmake step.
18:04:10: Starting: "/usr/bin/make"
/home/pete/Qt/5.9.1/gcc_64/bin/qmake -o Makefile ../AIQt/AIQt.pro -spec linux-g++ CONFIG+=debug CONFIG+=qml_debug
WARNING: Failure to find: ../src/stdafx.h
WARNING: Failure to find: ../src/Csound/csd.h
g++ -c -pipe -g -Wall -W -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_DATAVISUALIZATION_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../AIQt -I. -I../src -I../src/AIBase -I../src/Maths -I../src/Random -isystem /usr/local/include/csound -I../../../../Qt/5.9.1/gcc_64/include -I../../../../Qt/5.9.1/gcc_64/include/QtDataVisualization -I../../../../Qt/5.9.1/gcc_64/include/QtWidgets -I../../../../Qt/5.9.1/gcc_64/include/QtGui -I../../../../Qt/5.9.1/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I. -I../../../../Qt/5.9.1/gcc_64/mkspecs/linux-g++ -o main.o ../AIQt/main.cpp
In file included from /usr/include/c++/7/variant:35:0,
from ..###,
from ..###,
from ..###,
from ..###,
from ..###,
from ..###,
from ..###,
from ..###:
/usr/include/c++/7/bits/c++17_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2017 standard. This support must be enabled with the -std=c++17 or -std=gnu++17 compiler options.
#error This file requires compiler and library support \
^~~~~
In file included from ..###,
from ..###
from ..###,
from ..###,
from ..###,
from ..###,
from ..###:
../src/AIBase/Geno.h:70:18: error: ‘variant’ in namespace ‘std’ does not name a type
std::variant m_valueVariant;
^~~~~~~
In file included from ..###,
from ..###,
from ..###,
from ..###,
from ..###,
from ..###:
../src/AIBase/Pheno.h:22:13: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
const double getGenoValue(size_t genoIndex) const;
^~~~~
../src/AIBase/Pheno.h:24:13: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
const UserRating getRating() const;
^~~~~
In file included from ..###,
from ..###:
../AIRadioQt/GraphDialog.h:16:15: warning: declaration ‘struct ar::ai::ClusterList’ does not declare anything
class ar::ai::ClusterList;
^~~~~~~~~~~
make: *** [main.o] Error 1
18:04:13: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project AIQt (kit: Qt 5.9.1 GCC 64bit)
The kit Qt 5.9.1 GCC 64bit has configuration issues which might be the root cause for this problem.
When executing step "Make"
18:04:13: Elapsed time: 00:03.
回答:
正如 nwp 所说，我只需要清理并重建它。
另一位发帖人也评论说 CONFIG += c++17 似乎还不支持，所以需要使用 QMAKE_CXXFLAGS += -std=c++17 。不过他很快删除了他的评论，所以我无法亲自感谢他为我检查文档的努力。
最佳答案
CONFIG += c++17 可用于 Qt 5.12 及更高版本。
对于 Qt 5.11 及更早版本，it is not a recognized QMake flag而且你得弄脏你的手。
添加 QMAKE_CXXFLAGS += -std=c++17 为 GCC 和 Clang 完成工作；对于 MSVC，您将 probably need to specify /std:c++17 或 /std:c++latest.
关于c++ - 无法在 QtCreator 中使用 g++ 7.2 使用 c++17 功能，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46610996/