Why no std::byte in qt?!!

kenchan

@Engelard
OK, problem solved...
In spite the Microsoft docs which say the -std:c++17 flag can be used in VS2017 to enable the c++17 features it does not seem to work though the command line via qmake!
but adding...
DEFINES += _HAS_STD_BYTE
and
QMAKE_CXXFLAGS += -std:c++17
to the pro file does work and I can use std::byte in the code.

QMAKE_CXXFLAGS += -std:c++1z also worked

I hope this works for you too.

Engelard

@VRonin said in Why no std::byte in qt?!!:

@Engelard said in Why no std::byte in qt?!!:

still it says that byte is not part of std.

Did you #include <cstddef>?

Yes, i mentioned in firsts posts.

Can you open Visual Studio 2017, create a simple console program and test if it works there?

In first post i told that original program which widely using std::byte was from my VS2017(ofc it works).

@kshegunov

This is the CPU instruction set. Intel processors use amd64, so it's correct.

lol

Engelard

@kshegunov said in Why no std::byte in qt?!!:

@Engelard said in Why no std::byte in qt?!!:

there is compilers for amd chosen, when i have normal for intel i suppose in my VS

This is the CPU instruction set. Intel processors use amd64, so it's correct.

lol

@kkoehne said in Why no std::byte in qt?!!:

@Engelard said in Why no std::byte in qt?!!:

CONFIG += c++17
QMAKE_CXXFLAGS += -std:c++17

Please try

CONFIG +=c++1z

This works for me with Visual Studio 2017 compiler.

Sorry, no effect. Tried both of them, separately and together like in your message.

Engelard

@kenchan damn it worked! At least now after typing std::b it advice me byte type and word now not dead black but violet like all valid variables should be(finally).

But!)

It still rejects to compile. I tried to clean all, then rebuild, but same error:

alt text

Engelard

Even restart of Qt don't help, what's wrong...

kenchan

@Engelard
hmm?? looks like you have another problem somewhere.
Can you show us your pro file?
Can you show us a screen shot of your kits panel for the kit you are currently using again please?
Can you show us a screen shot the qt versions panel and the compilers panel again please?
Can can you show a screen shot of the compiler output when you compile your code with the std::byte declaration please?

Thank you

kenchan

@Engelard
I few tests show me that you can actually get away with using either DEFINES += _HAS_STD_BYTE or QMAKE_CXXFLAGS += -std:c++17 when using the VS 15.0 compiler.
Using both is obviously twice as safe.

Just make sure you blow away the build folder, rerun qmake and rebuild just to be sure.

creating a new Non-Qt Plain C++ project with this pro file

 TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt
DEFINES += _HAS_STD_BYTE
QMAKE_CXXFLAGS += -std:c++17
 
SOURCES += \
        main.cpp

and this c++ code worked fine for me.

#include <iostream>
#include <cstddef>
 
using namespace std;
 
int main()
{
    byte stdbyte;
    stdbyte = std::byte(0);
    byte *arr = new std::byte[2];
    arr[0] = std::byte(0x2a);
 
    cout << "Hello World!" << endl;
    return 0;
}

Why don't you try this and see if it works?

Engelard

This post is deleted!

Engelard

Seems the problem was in old build directory. After complete deletion of it - program finally compiles:

alt text

DAMN it was hard and so long. New features of new C++17 in Qt cost so much...

kenchan

@Engelard
Yes, that is what I suspected was the problem.
Glad you finally got it working.