230628-expected unqualified-id

eton@230628 在编译supra基于debian12 Qt5.15 tbb12 libtbb12/stable,now 2021.8.0-2 amd64 的时候遇到下面的问题。一直找不到实际的问题原因，指导发现下面几个github的链接，原来是符号冲突导致的。

1. 添加`QT_NO_KEYWORDS`到编译选项中;

TARGET_COMPILE_DEFINITIONS(SUPRA_GUI
    PRIVATE ${SUPRA_Lib_DEFINES}
        ${CAMPVIS_DEFINITIONS} NODE_EDITOR_STATIC QT_NO_KEYWORDS)

ref:

2. 将qt中的关键字替换为宏定义

signal: 替换为Q_SIGNALS

slots: 替换为Q_SLOTS

emit 替换为Q_EMIT

因为上面的内容

It tells Qt not to define the moc keywords signals, slots, and emit, because these names will be used by a 3rd party library, e.g. Boost. Then to continue using Qt signals and slots with the no_keywords flag, simply replace all uses of the Qt moc keywords in your sources with the corresponding Qt macros Q_SIGNALS (or Q_SIGNAL), Q_SLOTS (or Q_SLOT), and Q_EMIT.

ref:

Using Qt with 3rd Party Signals and Slots

3. 重新编译，因为supra中涉及到使用第三方库NodeEdit,这个也使用了Qt所以也需要做setp02的替换。

for i in `find  ./ -name "*.hpp"` ; do
    sed s/signals:/Q_SIGNALS:/g -i $i && \
    sed s/slots:/Q_SLOTS:/g -i $i && \
    sed s/emit:/Q_EMIT:/g -i $i;
done

1. `g++ -E /usr/include/oneapi/tbb/flow_graph.h > a.h` 查看实际生成的文件到底是否存在语法问题；

合并头文件得到的问题代码截取部分如下，其实可以看到是没有语法问题的。

namespace d1 {
# 190 "/usr/include/oneapi/tbb/profiling.h"
    inline void create_itt_sync(void* , const char* , const char* ) {}

    inline void call_itt_notify(notify_type , void* ) {}

    inline void call_itt_task_notify(notify_type , void* ) {}
# 226 "/usr/include/oneapi/tbb/profiling.h"
struct event {
    event(const std::string &) { } 

    void emit() { }

    static void emit(const std::string &) { }
};
}

但是这里学习到了namespace的注入功能

# 20 "/usr/include/oneapi/tbb/detail/_namespace_injection.h"
namespace tbb {} 

namespace oneapi {
namespace tbb = ::tbb;
}

目标是将::tbb等价于::oneapi::tbb 这样就可以兼容以前没有oneapi时候对tbb的命名空间的使用了.

ref:

2. 分析C++中到底'qualified'是什么意思

A qualified id-expression is an unqualified id-expression prepended by a scope resolution operator ::, and optionally, a sequence of any of the following separated by scope resolution operators

有人做如下翻译，这样理解相对容易

非受限id(Unqualified-id)

广义化的标识符(identifier)。它可以是前面的任何一种或者析构函数的名称(比如Date或者List)

受限id(qualified-id)

用一个类名或者名字空间对一个unqualified-id进行限定，或者使用全局作用域解析运算符::进行限定

这种名称可以是多次限定的

例子：::X，S::x，Array::y，::N::A:

ref: https://en.cppreference.com/w/cpp/language/qualified_lookup

3. search below info in bing.

oneapi/tbb/profiling.h:229:15: error: expected unqualified-id before ‘)’ token

get the resolution finally.

/usr/include/oneapi/tbb/profiling.h:229:15: error: expected unqualified-id before ‘)’ token

229 | void emit() { }

| ^

/usr/include/oneapi/tbb/profiling.h:231:22: error: expected unqualified-id before ‘const’

231 | static void emit(const std::string &) { }

| ^~~~~

/usr/include/oneapi/tbb/profiling.h:231:22: error: expected ‘)’ before ‘const’

231 | static void emit(const std::string &) { }

| ^~~~

| )

Qt代码中signals, slots, emit其实都是宏定义的关键字, "qobjectdefs.h" 中对与signals, slots, emit的解析最后都是empty,也就是最后macro在解析的时候如果遇到emit这个字符串，那么如果前面存在Qt的头引用，那么就会出现

# define emit

这样后面emit关键字变为‘NULL’这样就不符合C++的语法了，因为函数定义需要一个NAME ;
Recurrence issues

创建如下文件:

$ cat abc.cc
void fun(){}
void emit(){}
void fun3(){}

利用g++ -c进行编译

$ g++ -Demit='' -c  abc.cc
abc.cc:2:11: error: expected unqualified-id before ‘)’ token
    2 | void emit(){}
      |           ^

问题完整的复现，finish.

Appendix

full error log.

FAILED: src/GraphicInterface/CMakeFiles/SUPRA_GUI.dir/SUPRA_GUI_autogen/mocs_compilation.cpp.o
/usr/bin/g++ -DHAVE_BEAMFORMER -DHAVE_BEAMFORMER_MINIMUM_VARIANCE -DHAVE_CUDA -DHAVE_CUDA_CUBLAS -DHAVE_CUFFT -DHAVE_DEVICE_IGTL_OUTPUT -DHAVE_DEVICE_METAIMAGE_OUTPUT -DHAVE_DEVICE_TRACKING_IGTL -DHAVE_DEVICE_TRACKING_SIM -DHAVE_DEVICE_ULTRASOUND_SIM -DNODE_EDITOR_STATIC -DQT_CORE_LIB -DQT_GUI_LIB -DQT_WIDGETS_LIB -I/home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface -I/home/eton/00-src/supra/src/GraphicInterface -I/home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/SUPRA_GUI_autogen/include -I/home/eton/00-src/supra/src/GraphicInterface/SUPRA_GUI -I/home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/NodeEditor_install/include -I/home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/NodeEditor/include -I/home/eton/00-src/supra/src/GraphicInterface/private -I/include -I/home/eton/00-src/supra/src/SupraLib -I/home/eton/00-src/supra/src/SupraLib/utilities/jsoncpp -I/usr/include/openigtlink -isystem /home/eton/Qt/5.15.2/gcc_64/include -isystem /home/eton/Qt/5.15.2/gcc_64/include/QtWidgets -isystem /home/eton/Qt/5.15.2/gcc_64/include/QtGui -isystem /home/eton/Qt/5.15.2/gcc_64/include/QtCore -isystem /home/eton/Qt/5.15.2/gcc_64/./mkspecs/linux-g++ -DQT_QML_DEBUG -fopenmp -g -fPIC -std=gnu++11 -MD -MT src/GraphicInterface/CMakeFiles/SUPRA_GUI.dir/SUPRA_GUI_autogen/mocs_compilation.cpp.o -MF src/GraphicInterface/CMakeFiles/SUPRA_GUI.dir/SUPRA_GUI_autogen/mocs_compilation.cpp.o.d -o src/GraphicInterface/CMakeFiles/SUPRA_GUI.dir/SUPRA_GUI_autogen/mocs_compilation.cpp.o -c /home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/SUPRA_GUI_autogen/mocs_compilation.cpp
In file included from /usr/include/oneapi/tbb/spin_mutex.h:23,
                 from /usr/include/oneapi/tbb/flow_graph.h:26,
                 from /usr/include/tbb/flow_graph.h:17,
                 from /home/eton/00-src/supra/src/SupraLib/SupraManager.h:21,
                 from /home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/SUPRA_GUI_autogen/EWIEGA46WW/../../../../../supra/src/GraphicInterface/parameterWidget.h:3,
                 from /home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/SUPRA_GUI_autogen/EWIEGA46WW/moc_parameterWidget.cpp:10,
                 from /home/eton/00-src/build-supra-Desktop_Qt_5_15_2_GCC_64bit-Debug/src/GraphicInterface/SUPRA_GUI_autogen/mocs_compilation.cpp:6:
/usr/include/oneapi/tbb/profiling.h:229:15: error: expected unqualified-id before ‘)’ token
  229 |     void emit() { }
      |               ^
/usr/include/oneapi/tbb/profiling.h:231:22: error: expected unqualified-id before ‘const’
  231 |     static void emit(const std::string &) { }
      |                      ^~~~~
/usr/include/oneapi/tbb/profiling.h:231:22: error: expected ‘)’ before ‘const’
  231 |     static void emit(const std::string &) { }
      |                     ~^~~~~
      |                      )