VB.NET ERR: 0x8007000B (Bad Image Format Exception) -

__declspec(dllexport) void __cdecl  memcopy(void *pdst, const void *psrc, unsigned int nsize) {             __asm {                     mov esi, psrc                     mov edi, pdst                     mov ecx, nsize $l1:                     movq mm7, [esi]                     add esi, 8                     movq [edi], mm7                     add edi, 8                     dec ecx                     jne $l1             };  } 

this code copyblit8x8.dll

i imported .dll c++ console application , copied string 'hello world' char * a, char * b. echoed b succesfully showing 'hello world'.

then, generic memory copy routine accepts 2 pointers perform copy, did below;

the picture said post title ~ bad image format exception. err code: 0x8007000b.

this generic error little information applies variety of scenarios. but, can safely assume, pointers.

what want fast asm module perform generic memory copies,but vb.net images.

any tips, stack overflow!

a badimageformatexception thrown when try load assembly or dll compiled under different bitness application. instance if try load 32-bit dll in 64-bit application (or vice versa).

make sure dll compiled in same bitness application. if application compiled anycpu either force x86 or x64, or compile 2 dlls using each bitness, import each function (but different names) , call correct 1 after checking environment.is64bitprocess property.

this example of anycpu solution:

'32-bit dll <dllimport("copyblit8x8.dll")> _ public shared function memcopy(<insert parameters here>) end function  '64-bit dll <dllimport("copyblit8x8_x64.dll")> _ public shared function memcopy64(<insert parameters here>) end function  public sub dostuff()     if environment.is64bitprocess = true         memcopy64(...) 'call 64-bit dll     else         memcopy(...) 'call 32-bit dll     end if end sub 

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edit:

according hans passant, asm mmx instructions can't used in x64, solution above not work you. i'm leaving there because works dlls compiled using native c/c++ code.