Re: [Patch] SourceLevelDebugPkg/SecPeiDebugAgentLib: Fix duplicate symbol

[Andrew Fish <afish@apple.com>]

> On May 25, 2017, at 9:08 AM, Laszlo Ersek <lersek@redhat.com> wrote:
> 
> On 05/25/17 03:47, Kinney, Michael D wrote:
>> Andrew,
>> 
>> I think I have found an alternate fix for this XCODE5 specific
>> build failure.  Since there appears to be a difference in the 
>> linker behavior between MSFT/GCC/XCODE tool chains, I reviewed 
>> the 'ld' command line options used in XCODE5 tool chain in
>> tools_def.txt.
>> 
>> There is a flag set call '-all_load'.  The description of this
>> flag is 'Loads all members of static archive libraries.'.
>> 
>> I tried removing this flag from the XCODE5 specific SLINK_FLAGS
>> and DLINK_FLAGS statements in tools_def.txt, and the duplicate
>> symbol build failure is no longer present.  I am able to build
>> and boot OVMF with XCODE5 with -D SOURCE_DEBUG_ENABLE flag set.
>> 
>> This seems to make XCODE5 linker behavior match the MSFT and GCC
>> linker behavior.
>> 
>> Do you know why '-all_load' is used in XCODE5 and what impacts
>> there may be from removing it?
> 
> Please don't remove -all_load from there; instead we should figure out
> if the same can be brought to MSFT and GCC.
> 

Not to mention I was told by the Xcode linker developer that -all_load was required to ensure in all cases the Mach-O produced would be compatible with conversion to PE/COFF. 

Thanks,

Andrew Fish

> The error message that XCODE5 emitted caught a real bug (undefined
> behavior according to ISO C, see my previous email), and so we should
> keep that detection enabled (we should even extend it to other
> toolchains, if that's possible).
> 
> As for docs, I found this:
> 
> http://www.manpages.info/macosx/ld.1.html <http://www.manpages.info/macosx/ld.1.html>
> 
>> -all_load
>>    Loads all members of static archive libraries. This option does
>>    not apply to dynamic shared libraries.
> 
> 
> Thanks
> Laszlo