这里棘手的部分是 BUILD_DEBUG_CLASS_MEMBER 的定义 在 TestCompiler.cpp 中,我知道我可以简单地不定义它来解决错误(请参阅下面运行时结果中的断言)
我的问题是:
1. 为什么在我的例子中,虚拟内联函数被内联到 TestCompiler.obj 文件中
即使我不调用 delete 或 TriShape/Shape 的任何类方法。
2.为什么在运行时调用TestCompiler.o的内联版本
但不是 Class.o 中的另一个版本。 (不仅是下面的 rumtime 结果,gdb 也显示了它。)
无论如何,我在这里只是想研究一下为什么gcc会这样。 例如,它使 .obj 非常大,但它可能有助于尽可能多地内联 想要……!?我只是猜测,我不完全明白。 (因为我的错误(我愚蠢的定义)很明显,所以我不想说出来 是gcc的错误。 ;) )
顺便说一句,我测试过的编译器是 gcc 4.4.7 和 VS2013。 仅 前因断言。 而且,原始代码库在一个不是我的库中,并且 所以我无法轻易更改 Shape 文件。 (ClassA 是一种工厂,Shape 类是库的核心。)
非常感谢您的耐心等待,我期待着您的评论/回答。
我的程序(抱歉,还有一些额外的测试代码……;))
(ClassA 是一种工厂,Shape 类是源自库的核心。)
//================================================================//
// TestCompiler.cpp
//
//#include "stdafx.h"
#include <stdio.h>
#include "TestA.h"
#define BUILD_DEBUG_CLASS_MEMBER // :)
#include "TriShape.h" // include it just for testing compiler/linker in our case
int main(int argc, char* argv[])
{
printf("TC: main start \n");
//TestA::gTestAFunc();
gTestAFunc();
// calls to TriShape::testVFunc, etc
//...
printf("TC: main finish \n");
return 0;
}
//================================================================//
//TestA
#pragma once
extern void gTestAFunc();
//================================================================//
//TestA.cpp
#include <stdio.h>
#include "ClassA.h"
void gTestAFunc()
{
ClassA* pA = new ClassA();
pA->createS();
pA->removeS();
delete pA;
}
//================================================================//
//ClassA.h
#pragma once
#include "Shape.h"
class ClassA
{
public:
ClassA()
: m_pShape(NULL)
{
}
void createS();
void removeS();
Shape* m_pShape;
};
//================================================================//
//ClassA.cpp
#include <stdio.h>
#include "ClassA.h"
//#define BUILD_DEBUG_CLASS_MEMBER // don't define it :)
#include "TriShape.h"
void ClassA::createS()
{
m_pShape = new TriShape;
}
void ClassA::removeS()
{
delete m_pShape;
m_pShape = NULL;
}
//================================================================//
//Shape.h
#pragma once
class Shape //:: MemoryObject
{
public:
Shape()
: m_ptr(NULL)
{
printf("Shape ctor: this:%p size:%d \n", this, sizeof(*this));
}
//TODO: inline it! :P
virtual ~Shape()
{
//m_ptr
printf("Shape dtor: this:%p size:%d \n", this, sizeof(*this));
}
inline virtual int testVFunc()
{
return -1;
}
Shape* m_ptr;
};
//test ONLY:
//#include "TriShape.h"
//================================================================//
//TriShape.h
#pragma once
#include <assert.h>
#include "Shape.h"
#define FIX_NUM 0xABCD
class MyList
{
public:
MyList()
: m_dummy(FIX_NUM)
{
}
//TODO: inline it! :P
virtual ~MyList()
{
printf("List dtor: this:%p size:%d dummy:0x%x \n", this, sizeof(*this), m_dummy);
assert(m_dummy==FIX_NUM);
//#pragma message( "List dtor here" )
}
int m_dummy;
};
class TriShape : public Shape
{
public:
TriShape()
//: m_debugMember()
{
printf("TriShape ctor: this:%p size:%d \n", this, sizeof(*this));
}
#if 1
//caseT1
virtual ~TriShape();
#else
//caseT2
virtual ~TriShape()
{
printf("TriShape dtor IN class: this:%p size:%d \n", this, sizeof(*this));
#pragma message( "TriShape dtor here IN class" )
}
#endif
virtual int testVFunc();
#ifdef BUILD_DEBUG_CLASS_MEMBER
MyList m_debugMember;
#endif
};
// inline dtor
#if 1
inline TriShape::~TriShape()
{
printf("TriShape dtor AFTER class: this:%p size:%d \n", this, sizeof(*this));
#pragma message( "TriShape dtor here AFTER class" )
#ifdef BUILD_DEBUG_CLASS_MEMBER
#pragma message("\tit is defined: BUILD_DEBUG_CLASS_MEMBER")
#endif
}
#endif
// inline virutal func
inline int TriShape::testVFunc()
{
printf("TriShape testVFunc AFTER class: this:%p size:%d \n", this, sizeof(*this));
#pragma message( "TriShape testVFunc here AFTER class" )
#ifdef BUILD_DEBUG_CLASS_MEMBER
#pragma message("\tit is defined: BUILD_DEBUG_CLASS_MEMBER")
#endif
return 0;
}
运行时输出
$ ./inlineTest
TC: main start
Shape ctor: this:0x995b018 size:8
TriShape ctor: this:0x995b018 size:8
TriShape dtor AFTER class: this:0x995b018 size:16
List dtor: this:0x995b020 size:8 dummy:0x20fe1
inlineTest: TriShape.h:22: virtual MyList::~MyList(): Assertion
`m_dummy==0xABCD' failed.
Aborted (core dumped)
由 -S 生成的可读目标代码,表明它内联在 BOTH .asm 中
In TestCompiler.asm:
The destructor is inlned up this section
.section .text._ZN8TriShapeD1Ev,"axG",@progbits,_ZN8TriShapeD1Ev,comdat
(...)
call _ZN6MyListD1Ev
(...)
call _ZN5ShapeD2Ev
In ClassA.asm:
The destructor is inlned up this section
.section .text._ZN8TriShapeD1Ev,"axG",@progbits,_ZN8TriShapeD1Ev,comdat
(...)
call _ZN5ShapeD2Ev
在链接器生成的映射文件中(grep around TriShape dtor 的结果)
.text._ZN8TriShapeD1Ev
0x0000000000000000 0x0 ClassA.o
.text._ZN8TriShapeD0Ev
0x0000000000000000 0x0 ClassA.o //oops, ALL ZEROS means something??
(...)
.rel.text._ZN8TriShapeD1Ev
0x0000000000000000 0x0 /usr/lib/../lib/crt1.o
.rel.text._ZN8TriShapeD0Ev
0x0000000000000000 0x0 /usr/lib/../lib/crt1.o
(...)
.text._ZN8TriShapeD1Ev
0x0000000008048a80 0xb9 TestCompiler.o
0x0000000008048a80 _ZN8TriShapeD1Ev
*fill* 0x0000000008048b39 0x1 90909090
.text._ZN8TriShapeD0Ev
0x0000000008048b3a 0xb9 TestCompiler.o
0x0000000008048b3a _ZN8TriShapeD0Ev
*fill* 0x0000000008048bf3 0x1 90909090
最佳答案
不幸的是,您违反了 TriShape
的单一定义规则,因此试图猜测编译器为何执行特定操作的原因不太可能产生有用的信息。允许编译器假设类和函数在所有源文件中都是相同的,因此它可以选择一个并在所有地方执行该代码。
关于c++ - gcc : inline of virtual function and especially destructor in my case 中内联的行为,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31004979/