Re: [問題] 關於Class指標的觀念
看板C_and_CPP (C/C++)作者descent (「雄辯是銀，沉默是金」)時間11年前 (2013/08/30 11:54)推噓0(0推 0噓 5→)留言5則, 2人參與討論串11/19 (看更多)
vc 版本, 運氣很好, 沒花太久時間。
vc 我不熟, 有什麼問題還請版友們提出。
env:
vc2010
winxp 32bit
#include <iostream>
#include <cstdio>
using namespace std;
struct A
{
virtual void func()
{
printf("i: %d\n", i_);
}
void inc()
{
++i_;
}
A()
{
i_=10;
}
private:
int i_;
};
int main()
{
void (A::*p)() = &A::func;
//cout << "sizeof: " << sizeof(p) << endl;
//cout << "sizeof: " << sizeof(A) << endl;
//printf("addr: %p\n", p);
//cout << "p:" << p << endl;
//unsigned int addr = pp;
//printf("addr: %p\n", pp);
A a;
(a.*p)();
unsigned int vptr_addr = *(unsigned int *)&a;
cout << "vptr_addr:" << hex << vptr_addr << endl;
unsigned int func_addr = *(unsigned int *)vptr_addr;
cout << "func_addr:" << hex << func_addr << endl;
a.inc();
__asm
{
lea ecx, a
}
#if 1
(*(void(*)())(func_addr) )();
A aa;
__asm
{
lea ecx, aa
}
(*(void(*)())(func_addr) )();
__asm
{
lea ecx, a
}
(*(void(*)())(func_addr) )();
__asm
{
lea ecx, aa
}
(*(void(*)())(func_addr) )();
#endif
return 0;
}
C:\>cl□ c.cpp
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 for
80x86
Copyright (C) Microsoft Corporation.□ All rights reserved.
c.cpp
C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xlocale(323) :
warning
C4530: 已使用 C++ 例外處理常式，但沒有啟用回溯語意 (Unwind Semantics)。請指定
/E
Hsc
Microsoft (R) Incremental Linker Version 10.00.30319.01
Copyright (C) Microsoft Corporation.□ All rights reserved.
/out:c.exe
c.obj
C:\>c
i: 10
vptr_addr:41a1bc
func_addr:4011a0
i: 11
i: 10
i: 11
i: 10
順便測試了 arm/g++
arm version by c++
c.arm: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked
(uses shared libs), for GNU/Linux 2.6.26, not stripped
root@/home$ ./c.arm
i: 10
vptr_addr:8cc8
func_addr:8b74
i: 11
i: 10
i: 11
i: 10
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