The title is pretty self-descriptive. I've downloaded Qt Creator 2.7.0, and I am trying to compile some basic C++11 code:
int my_array[5] = {1, 2, 3, 4, 5};
for(int &x : my_array)
{
x *= 2;
}
I'm receiving the following error:
range based for loops are not allowed in c++ 98 mode
Yet, according to this article this version of Qt Creator supports C++11. So how do I enable it?
According to this site add
CONFIG += c++11
to your .pro file (see at the bottom of that web page). It requires Qt 5.
The other answers, suggesting
QMAKE_CXXFLAGS += -std=c++11 (or QMAKE_CXXFLAGS += -std=c++0x)
also work with Qt 4.8 and gcc / clang.
-std=c++11 to the linker flags which looks weird to me. –
Russ ranged-based 'for' loops are not allowed in C++ 98 mode appears when using for(auto& x : xs) (xs is a vector of strings). Also std::vector<std::string> xs = { "a", "b", "c" }; issues an error about being unable to convert from brace-enclosed initializer list to std::vector<std::basic_string<char> >.These along with other errors and warnings (auto -> ISO C++ forbids declaration with no type) are all C++11 related.It works only when both QMAKE_CXXFLAGS+= -std=c++11 and QMAKE_LFLAGS += -std=c++11 are in the project file. It's so much easier to do these things in CMake...Geeesh... –
Tuesday -std=c++11 to the linker flags resolves these error messages: It looks like a bug in qmake. Could you somehow post an SSCCE, please? (E.g. a github gist.) –
Russ QMAKE_CXXFLAGS += -std=c++11 should work with Qt 4.8 without QMAKE_LFLAGS += -std=c++11. I still think that it is a bug in qmake if you have to add std=c++11 to the linker flags. Or I am missing your point... :( –
Russ CONFIG += c++11 doesn't work, Qt still defaults to -std=c++0x as shown in the compile output –
Flatcar -std=c++0x. That's why I also mention that flag in my answer. –
Russ QMAKE_CXXFLAGS += -std=c++11 does help. So the question is, why is Qt defaulting to the wrong one when explicitly told through CONFIG? –
Flatcar -std=c++0x should work even if the compiler supports -std=c++11 too. So, in my opinion, Qt does the right thing and defaults to the flag that should always work (even with pre-C+11 compilers). What happens if you use -std=c++0x? Doesn't your C++11 compiler recognize that flag? Or what sort of error do you get? –
Russ functional that won't compile with -std=c++0x but will with -std::c++11 so my errors are undefined functions and namespaces. Also since when has ignoring a users explicit make setting "the right thing to do"? I've had to override their value using QMAKE_CXXFLAGS_CXX11 = -std=c++11 –
Flatcar -std=c++11, then it should also support (the deprecated) -std=c++0x flag as well, and both flags are supposed to have identical effects (which apparently isn't the case on your machine). If a compiler supports -std=c++0x, it doesn't mean that it understands -std=c++11. Therefore, picking -std=c++0x as default for C++11 compatibility mode is a reasonable choice. On my machine, at least according to the man page, -std=c++0x and -std=c++11 are identical. –
Russ -std=c++11 if the compiler supports it, and Qt could be smart enough to do so. Well, if this issue hurts you that much, you could file a bug report... –
Russ Add this to your .pro file
QMAKE_CXXFLAGS += -std=c++11
or
CONFIG += c++11
As an alternative for handling both cases addressed in Ali's excellent answer, I usually add
# With C++11 support
greaterThan(QT_MAJOR_VERSION, 4){
CONFIG += c++11
} else {
QMAKE_CXXFLAGS += -std=c++0x
}
to my project files. This can be handy when you don't really care much about which Qt version is people using in your team, but you want them to have C++11 enabled in any case.
add to your qmake file
QMAKE_CXXFLAGS+= -std=c++11
QMAKE_LFLAGS += -std=c++11
If you are using an earlier version of QT (<5) try this
QMAKE_CXXFLAGS += -std=c++0x
The only place I have successfully make it work is by searching in:
...\Qt\{5.9; or your version}\mingw{53_32; or your version}\mkspecs\win32-g++\qmake.conf:
Then at the line:
QMAKE_CFLAGS += -fno-keep-inline-dllexport
Edit :
QMAKE_CFLAGS += -fno-keep-inline-dllexport -std=c++11
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