当宏用作变量名时，是否有任何方法可以跳过宏替换(在预处理期间）

Is there any way to skip macro replacement(During preprocessing) when macro is used as a variable name?

本文关键字：替换 预处理 方法 变量名 是否 任何      更新时间：2023-10-16

ConflictHeader.h

      #define _c 6 //This is third party header, canot change, since
// there is no sorce code to rebuild

测试类.h

    #ifndef TESTCLASS_H
    #define TESTCLASS_H
    #include <QObject>
    #include "ConflictHeader.h"//Include conflicted header
    class TestClass : public QObject
    {
      Q_OBJECT
    public:
        TestClass(QObject *parent);
        ~TestClass();
    private:
    };
    #endif // TESTCLASS_H

testclass.cpp

#include "testclass.h"
TestClass::TestClass(QObject *parent)
  : QObject(parent)
{
}    
TestClass::~TestClass()
{
}

moc_testclass.cpp

这是由MOC编译器生成的，请注意编译问题所在的函数"int TestClass:：qt_metacall(QMetaObject:：Call_c，int _id，void**_a(">

/****************************************************************************
** Meta object code from reading C++ file 'testclass.h'
**
** Created: Wed Jun 10 11:24:06 2015
**      by: The Qt Meta Object Compiler version 62 (Qt 4.7.4)
**
** WARNING! All changes made in this file will be lost!
*****************************************************************************/
#include "../../testclass.h"
#if !defined(Q_MOC_OUTPUT_REVISION)
#error "The header file 'testclass.h' doesn't include <QObject>."
#elif Q_MOC_OUTPUT_REVISION != 62
#error "This file was generated using the moc from 4.7.4. It"
#error "cannot be used with the include files from this version of Qt."
#error "(The moc has changed too much.)"
#endif
QT_BEGIN_MOC_NAMESPACE
static const uint qt_meta_data_TestClass[] = {
 // content:
       5,       // revision
       0,       // classname
       0,    0, // classinfo
       0,    0, // methods
       0,    0, // properties
       0,    0, // enums/sets
       0,    0, // constructors
       0,       // flags
       0,       // signalCount
       0        // eod
};
static const char qt_meta_stringdata_TestClass[] = {
    "TestClass"
};
const QMetaObject TestClass::staticMetaObject = {
    { &QObject::staticMetaObject, qt_meta_stringdata_TestClass,
      qt_meta_data_TestClass, 0 }
};
#ifdef Q_NO_DATA_RELOCATION
const QMetaObject &TestClass::getStaticMetaObject() { return staticMetaObject; }
#endif //Q_NO_DATA_RELOCATION
const QMetaObject *TestClass::metaObject() const
{
    return QObject::d_ptr->metaObject ? QObject::d_ptr->metaObject : &staticMetaObject;
}
void *TestClass::qt_metacast(const char *_clname)
{
    if (!_clname) return 0;
    if (!strcmp(_clname, qt_meta_stringdata_TestClass))
        return static_cast<void*>(const_cast< TestClass*>(this));
    return QObject::qt_metacast(_clname);
}
int TestClass::qt_metacall(QMetaObject::Call _c, int _id, void **_a)
{
    _id = QObject::qt_metacall(_c, _id, _a);
    if (_id < 0)
        return _id;
    return _id;
}
QT_END_MOC_NAMESPACE

编译器输出错误1>。\GeneratedFiles\Debug\moc_testclass.cpp(62(：错误C2143:语法错误：在"常量"之前缺少"(">

因此，我无法更改"ConflictHeader.h"(第三方库(和"moc_testclass.cpp"(moc生成(中的"_c"。

当宏用作变量名时，是否有任何方法可以跳过宏替换(在预处理期间(

您应该能够通过使用来解决该问题

#include "ConflictHeader.h"//Include conflicted header
#ifdef _c
#undef _c
#endif

一个更好的选择可能是为ConflictHeader.h创建一个wrapper.h文件，并在代码的其余部分使用wrapper.h文件。

ConflictHeaderW.h:

#pragma once
#include "ConflictHeader.h"
#ifdef _c
#undef _c
#endif
// #undef anything else that create problems.

使用#undef预处理器指令来取消定义宏。

更多信息：https://gcc.gnu.org/onlinedocs/cpp/Undefining-and-Redefining-Macros.html

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