Fish:

From: afish@apple.com [mailto:afish@apple.com]
Sent: Thursday, June 6, 2019 11:39 AM
To: devel@edk2.groups.io; Lu, XiaoyuX <xiaoyux.lu@intel.com>
Cc: Gao, Liming <liming.gao@intel.com>; Bi, Dandan <dandan.bi@intel.com>; Wang, Jian J <jian.j.wang@intel.com>
Subject: Re: [edk2-devel] [PATCH v1 1/1] CryptoPkg/IntrinsicLib: Fix CLANG38 IA32 build problem

On Jun 4, 2019, at 11:33 PM, Xiaoyu Lu <xiaoyux.lu@intel.com> wrote:

Hi Liming,

-----Original Message-----
From: Gao, Liming
Sent: Wednesday, June 5, 2019 1:57 PM
To: devel@edk2.groups.io; Lu, XiaoyuX <xiaoyux.lu@intel.com>
Cc: Bi, Dandan <dandan.bi@intel.com>; Wang, Jian J <jian.j.wang@intel.com>
Subject: RE: [edk2-devel] [PATCH v1 1/1] CryptoPkg/IntrinsicLib: Fix
CLANG38 IA32 build problem

Xiaoyu:

-----Original Message-----
From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of
Xiaoyu Lu
Sent: Wednesday, June 05, 2019 1:25 PM
To: devel@edk2.groups.io
Cc: Lu, XiaoyuX <xiaoyux.lu@intel.com>; Bi, Dandan

<dandan.bi@intel.com>;

Wang, Jian J <jian.j.wang@intel.com>
Subject: [edk2-devel] [PATCH v1 1/1] CryptoPkg/IntrinsicLib: Fix CLANG38
IA32 build problem

When use clang-3.8 to build the NetworkPkg, compiler optimization
may use memcpy for memory copy. For example:

CryptoPkg/Library/OpensslLib/openssl/ssl/ssl_rsa.c:918: undefined
reference to `memcpy'`

Compiler optimization is sophisticated, but we can work around it
use __attribute__((__used__)) to informs the compiler that symbol
should be retained in the object file, even if it may be
unreferenced.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Signed-off-by: Xiaoyu Lu <xiaoyux.lu@intel.com>
---
CryptoPkg/Library/IntrinsicLib/CopyMem.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/CryptoPkg/Library/IntrinsicLib/CopyMem.c
b/CryptoPkg/Library/IntrinsicLib/CopyMem.c
index e29b4918d200..7faf5a34d8c1 100644
--- a/CryptoPkg/Library/IntrinsicLib/CopyMem.c
+++ b/CryptoPkg/Library/IntrinsicLib/CopyMem.c
@@ -10,8 +10,21 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
#include <Base.h>
#include <Library/BaseMemoryLib.h>

+#if defined(__clang__) && !defined(__APPLE__)

So, this change is only for CLANG tool chain.

+
+/* Copies bytes between buffers */
+static __attribute__((__used__))

What purpose for static?

Because I want __memcpy only use in this file scope.

+void * __memcpy (void *dest, const void *src, unsigned int count)
+{
+  return CopyMem (dest, src, (UINTN)count);
+}
+__attribute__((__alias__("__memcpy")))
+void * memcpy (void *dest, const void *src, unsigned int count);

__memcpy is IA32 Intrinsic API, memcpy is X64 Intrinsic API, right?

__memcpy isn't IA32 Intrinsic API, only memcpy is intrinsic API for both IA32 and X64.

The reason I alias memcpy and use __attribute__((__used__)) is let compiler retain symbol in object file,
So it can link correct.

Is this correct?

I think this is a bug in clang that requires the __used__, we hit something like this with Xcode too. If the compiler emits the intrinsic it should tell the linker and some how that was getting missed. Thus the __used__ is a work around. 

OK. It is for CLANG 3.8. I will check whether the latest CLANG8.0 fixes it.

Thanks,

Andrew Fish

Thanks
Liming

+
+#else
/* Copies bytes between buffers */
void * memcpy (void *dest, const void *src, unsigned int count)
{
 return CopyMem (dest, src, (UINTN)count);
}
+#endif
--
2.7.4