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POGet function address from a function structure member
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  1. POGet function address from a function structure member
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    copied!<p>I'm trying to get function addresses which are hidden behind structures. Unfortunately, the <b><code>void*</code></b> basic C++ conversion doesn't work, so I used <b><code>C++ template</code></b> instead.</p> <p><b>1. Basic </b><b><code>void*</code></b> <b>C++ conversion doesn't work with functions inside structures, why?</b></p> <pre><code>void * lpfunction; lpfunction = scanf; //OK lpfunction = MessageBoxA; //OK </code></pre> <p>I made a simple structure :</p> <pre><code>struct FOO{ void PRINT(void){printf("bla bla bla");} void SETA(int){} //nothing you can see void SETB(int){} //nothing you can see int GETA(void){} //nothing you can see int GETB(void){} //nothing you can see }; /////////////////////////////////////////// void *lpFunction = FOO::PRINT; </code></pre> <p>And the compiling error :</p> <pre><code>error C2440: 'initializing' : cannot convert from 'void (__thiscall FOO::*)(void)' to 'void *' </code></pre> <p><strong>2. Is getting function member addresses impossible?</strong></p> <p>Then, I made a template function which is able to convert a function member to address. Then I will call it by assembly. It should be something like this: </p> <pre><code>template &lt;class F,void (F::*Function)()&gt; void * GetFunctionAddress() { union ADDRESS { void (F::*func)(); void * lpdata; }address_data; address_data.func = Function; return address_data.lpdata; //Address found!!! } </code></pre> <p>And here is the code : </p> <pre><code>int main() { void * address = GetFunctionAddress&lt;FOO,&amp;FOO::PRINT&gt;(); FOO number; number.PRINT(); //Template call void * lpdata = &amp;number; </code></pre> <p><b></p> <pre><code> __asm mov ecx, lpdata //Attach "number" structure address __asm call address //Call FOO::PRINT with assembly using __thiscall </code></pre> <p></b></p> <pre><code>printf("Done.\n"); system("pause"); return 0; } </code></pre> <p>But, I see it is <strong>extremely specific</strong>. It looks like <strong>LOCK - KEY</strong>, and I have to make a new template for every set of argument types.</p> <p>Original (OK) :</p> <pre><code>void PRINT(); //void FOO::PRINT(); </code></pre> <p>Modify a bit :</p> <pre><code>void PRINT(int); //void FOO::PRINT(int); </code></pre> <p>Immediately with old template code the compiler shows : </p> <pre><code>//void (F::*func)(); //address_data.func = Function; </code></pre> <p><b></p> <pre><code>error C2440: '=' : cannot convert from 'void (__thiscall FOO::*)(int)' to 'void (__thiscall FOO::*)(void)' </code></pre> <p></b></p> <p><b>Why?</b> They are only addresses.</p> <pre><code>69: address_data.func = Function; 00420328 mov dword ptr [ebp-4],offset @ILT+2940(FOO::PRINT) (00401b81) </code></pre> <p>...</p> <p>EDIT3 : I know the better solution :</p> <pre><code>void(NUMBER::*address_PRINT)(void) = FOO::PRINT; int(NUMBER::*address_GETA)(void) = FOO::GETA; int(NUMBER::*address_GETB)(void) = FOO::GETB; void(NUMBER::*address_SETA)(int) = FOO::SETA; void(NUMBER::*address_SETA)(int) = FOO::SETB; </code></pre> <p>It's much better than <strong>template</strong>. And by the way I want to achieve the goal :</p> <pre><code>&lt;special_definition&gt; lpfunction; lpfunction = FOO::PRINT; //OK lpfunction = FOO::GETA; //OK lpfunction = FOO::GETB; //OK lpfunction = FOO::SETA; //OK lpfunction = FOO::SETB; //OK </code></pre> <p><strong>Is this possible?</strong></p>
 

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