moc.exe cannot parse double quotes in c++ raw string correctly

kagami 0

I have a very simple class TestRawString that inherits from QObject and I'm running into the infamous 'undefined reference to vtable' error in the constructor and destructor of TestRawString.

The moc build step to generate moc_TestRawString.cpp results in the following:
TestRawString.h:0:1: note: No relevant classes found. No output generated.
and indeed, moc_TestRawString.cpp is an empty file.

Once I comment the variable "raw_double_quotes" in TestRawString.h, the project will compile and run correctly. Is it a feature or something?

This phenomenon is easy to reproduce and here are my example codes.

TestRawString.h

#include <QObject>
class TestRawString : public QObject
{
    Q_OBJECT
public:
    explicit TestRawString(QObject *parent = nullptr);
    std::string raw_double_quotes = R"++(")++";
    std::string raw_single_quote = R"++(')++";
    std::string normal_double_quotes = "\"";
};

TestRawString.cpp (generated by Qt)

#include "TestRawString.h"

TestRawString::TestRawString(QObject *parent)
    : QObject{parent}
{}

main.cpp

#include "TestRawString.h"

int main()
{
    TestRawString trs;
    assert(trs.normal_double_quotes == R"++(")++");
    return 0;
}

.pro

QT -= gui

CONFIG += c++11 console
CONFIG -= app_bundle

HEADERS += \
    TestRawString.h

SOURCES += \
        TestRawString.cpp \
        main.cpp

enviroment:

Qt: (online installation)
QMake version 3.1
Using Qt version 6.2.4 in C:/Qt/Qt6.2/6.2.4/mingw_64/lib

compiler: gcc version 11.2.0 (x86_64-posix-seh-rev3, Built by MinGW-W64 project)

os: windows 10 21H2 x86_64

JKSH

@kagami-0 said in moc.exe cannot parse double quotes in c++ raw string correctly:

Is it a feature or something?

It's a limitation of moc.

As a workaround, initialize the raw string in a .cpp file, or use a non-raw escaped string.