On Sep 29, 2014, at 7:08 AM, J. E. <[email protected]> wrote:
> All good now, thanks for clarifying.
> I have converted the code to pointers and it is now compiling again.
>
> Seems like an odd limitation though, could we actually just provide memcpy to
> the compiler?
> (I'm no expert, just wandering)
>
Compiler intrinsics are not standardized and can be different for different
compilers. On IA32 64-bit math also causes intrinsics to be emitted. So a long
time ago we decided to not provide the per compiler intrinsics.
Thanks,
Andrew Fish
> From: [email protected]
> Date: Mon, 29 Sep 2014 06:34:47 -0700
> To: [email protected]
> Subject: Re: [edk2] Compiler inserting memcpy. Unresolved external symbol
> memcpy
>
>
> On Sep 29, 2014, at 5:39 AM, Scott Duplichan <[email protected]> wrote:
>
> J. E. [mailto:[email protected]] wrote:
>
> Sent: Monday, September 29, 2014 03:24 AM
> To: [email protected]
> Subject: [edk2] Compiler inserting memcpy. Unresolved external symbol memcpy
>
> I'm getting this error when compiling my project in X64. (But no error in
> NT32 for some reason, probably a 32bit vs 64bit thing).
>
> error LNK2001: unresolved external symbol memcpy
>
> I don't use memcpy at all, I only use CopyMem.
> So it must be the compiler optimizing code and inserting memcpy here and
> there.
>
> I added compile option /FAcs
> I found 20+ instances of memcpy.
>
> Is there a trick around this so I don't have to modify lots of code?
>
> This is a real problem with no easy solution that I know of. My rant: Why
> doesn't EDK2 provide
> just memcpy, etc?
> For your code, passing &rcDest instead of rcDest should eliminate the memcpy
> calls you show.
>
> Thanks,
> Scott
>
> If there is no way around it, should I not be parsing STRUCTS through
> functions and use pointers instead?
>
>
> Yes.
>
> UEFI 2.4 2.3.4.2 Detailed Calling Conventions
> The caller passes the first four integer arguments in registers. The integer
> values are passed from left to right in Rcx, Rdx, R8, and R9 registers. The
> caller passes arguments five and above onto the stack. All arguments must be
> right-justified in the register in which they are passed. This ensures the
> callee can process only the bits in the register that are required.
> The caller passes arrays and strings via a pointer to memory allocated by the
> caller. The caller passes structures and unions of size 8, 16, 32, or 64 bits
> as if they were integers of the same size. The caller is not allowed to pass
> structures and unions of other than these sizes and must pass these unions
> and structures via a pointer.
> …
>
> Thus the memcpy is the compiler enforcing the calling conventions.
>
> RECT A, B;
>
> A = B;
>
> Will also cause memcpy to be emitted.
>
> Thanks,
>
> Andrew Fish
>
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