[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 at 12 
> <mailto:_InterlockedCompareExchange at 12>
> .text:7C8097A2 _InterlockedCompareExchange at 12 
> <mailto:_InterlockedCompareExchange at 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 at 12 
> <mailto:_InterlockedCompareExchange at 12> endp
> ------------------------------------------------------------------------
>
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