Re: [ros-dev] question about InterlockedCompareExchange.

[Thomas Bluemel]

Learn x86 asm first... return values are returned in eax/rax

Thomas

Jack Yi wrote:
>   question about InterlockedCompareExchange.
>   
>  MSDN says: The function returns the initial value of the destination.
>  I just don't understand, why can we get the initial value of 
>  destination as return value by 'return 0Ch' ?
>  Thank you!
>   
>   
>  .text:7C8097A2 ; PVOID __stdcall InterlockedCompareExchange(PVOID 
>  *Destination,PVOID Exchange,PVOID Comperand)
>  .text:7C8097A2                 public _InterlockedCompareExchange@12 
>  <mailto:_InterlockedCompareExchange@12>
>  .text:7C8097A2 _InterlockedCompareExchange@12 
>  <mailto:_InterlockedCompareExchange@12> proc near
>  .text:7C8097A2                                         ; CODE XREF: 
>  BaseComputeProcessDllPath(x,x)+97B3p
>  .text:7C8097A2                                         ; 
>  CreateActCtxW(x)+15D2Dp
>  .text:7C8097A2
>  .text:7C8097A2 Destination     = dword ptr  4
>  .text:7C8097A2 Exchange        = dword ptr  8
>  .text:7C8097A2 Comperand       = dword ptr  0Ch
>  .text:7C8097A2
>  .text:7C8097A2                 mov     ecx, [esp+Destination]
>  .text:7C8097A6                 mov     edx, [esp+Exchange]
>  .text:7C8097AA                 mov     eax, [esp+Comperand]
>  .text:7C8097AE
>  .text:7C8097AE loc_7C8097AE:                           ; DATA XREF: 
>  .data:7C884014o
>  .text:7C8097AE                 lock cmpxchg [ecx], edx
>  .text:7C8097B2                 retn    0Ch
>  .text:7C8097B2 _InterlockedCompareExchange@12 
>  <mailto:_InterlockedCompareExchange@12> endp
>  ------------------------------------------------------------------------
>
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