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

[Laszlo Ersek <lersek@redhat.com>]

On 05/25/17 21:55, Ard Biesheuvel wrote:
> On 25 May 2017 at 11:06, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 05/25/17 19:38, Kinney, Michael D wrote:
>>> Laszlo,
>>>
>>> I think the equivalent flag for GCC builds is --whole-archive.
>>>
>>> I tried adding that flag to DLINK_FLAGS in GCC5, and I get the
>>> following error building OVMF from edk2/master with
>>> -D SOURCE_DEBUG_ENABLE set.
>>>
>>> DxeLoad.obj (symbol from plugin): In function `InstallIplPermanentMemoryPpis':
>>> (.text+0x0): multiple definition of `mMemoryDiscoveredNotifyList'
>>> SecPeiDebugAgentLib.obj (symbol from plugin):(.text+0x0): first defined here
>>> collect2: error: ld returned 1 exit status
>>
>> Great find! That's the error message we should get.
>>
>> Unfortunately, after reading the "ld" manual on "--whole-archive", it
>> seems that the complete object files will actually be copied into the
>> resultant binary, even if several of their symbols will remain unused. I
>> think that's quite sub-optimal. (I haven't verified this though.) What
>> we'd like to get is (a) the full verification at link time, and (b)
>> inclusion of *only* those symbols that are actually necessary.
>>
>> In your testing, when you build OVMF with and without "--whole-archive",
>> do you see a difference in, say, the DXEFV footprint, when the build
>> completes?
>>
>> (If so, then I wonder if we should add "--whole-archive" only to the
>> NOOPT build... Not sure.)
>>
> 
> I haven't tried, but I would expect --gc-sections to deal with the
> unused objects.

Good point! (... After I read this option's description too, in the "ld"
manual.) This ELF and PE/COFF stuff is way too complex for my taste. :/

Laszlo