Re: [edk2-devel] OvmfPkgX64 doesn't build with CLANG38 (clang 14.0.3) NOOPT - undefined reference to `memcpy'

["Yao, Jiewen" <jiewen.yao@intel.com>]

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Hi
Would you please use CopyMem() for the structure assignment?
VgpuGop->GopModeInfo  = *GopModeInfo;

That is best known method to resolve memcpy symbol issue.

Thank you
Yao Jiewen


From: Pedro Falcato <pedro.falcato@gmail.com>
Sent: Thursday, May 26, 2022 1:01 AM
To: Ard Biesheuvel <ardb@kernel.org>
Cc: edk2-devel-groups-io <devel@edk2.groups.io>; Rebecca Cran <quic_rcran@quicinc.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>; Yao, Jiewen <jiewen.yao@intel.com>; Justen, Jordan L <jordan.l.justen@intel.com>; Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [edk2-devel] OvmfPkgX64 doesn't build with CLANG38 (clang 14.0.3) NOOPT - undefined reference to `memcpy'

On Wed, May 25, 2022 at 5:45 PM Ard Biesheuvel <ardb@kernel.org<mailto:ardb@kernel.org>> wrote:
On Wed, 25 May 2022 at 18:44, Pedro Falcato <pedro.falcato@gmail.com<mailto:pedro.falcato@gmail.com>> wrote:
>
>
>
> On Wed, May 25, 2022 at 4:50 PM Ard Biesheuvel <ardb@kernel.org<mailto:ardb@kernel.org>> wrote:
>>
>> On Wed, 25 May 2022 at 17:08, Rebecca Cran <quic_rcran@quicinc.com<mailto:quic_rcran@quicinc.com>> wrote:
>> >
>> > I noticed OvmfPkg/OvmfPkgX64.dsc doesn't build with `-t CLANG38 -b
>> > NOOPT` (with clang version 14.0.2) with the latest edk2 master
>> > (07c0c2eb0a5970db614ebce1060fc79d6904bdfd):
>> >
>> > make: Nothing to be done for 'tbuild'.
>> > /usr/bin/ld: /usr/bin/ld: DWARF error: invalid or unhandled FORM value:
>> > 0x23
>> > /home/bcran/src/upstream/uefi/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/OvmfPkg/VirtioGpuDxe/VirtioGpu/OUTPUT/VirtioGpuDxe.lib(Gop.obj):
>> > in function `GopSetMode':
>> > Gop.c:(.text.GopSetMode+0x418): undefined reference to `memcpy'
>>
>> Can you dump the object file to see where the memcpy() call is emitted?
>
> I think I found the smoking gun: https://github.com/tianocore/edk2/blob/916f90baa547b3ebef8fa87c530e2f0c8e35e1e3/OvmfPkg/VirtioGpuDxe/Gop.c#L512

Indeed. We don't support struct assignment in Tianocore code, exactly
for this reason.
Note: We should think about providing some basic libc functions in base EDK2 as some are required by the clang/GCC compilers (see https://gcc.gnu.org/onlinedocs/gcc/Standards.html, grep for memcpy or freestanding).
Passing -ffreestanding would also be a good idea as to let the compiler know it's dealing with a freestanding environment vs a hosted user-space one.

All the best,
Pedro

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