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

["Kinney, Michael D" <michael.d.kinney@intel.com>]

Laszlo,

The other idea I have is for MSFT tool chains to do the DLINK step twice.  Once
with /WHOLEARCHIVE set to a .dll that is not used in later steps, but the doing 
the DLINK action detects duplicate symbols.

If the first DLINK step passes, then so a second DLINK step to a .dll without 
/WHOLEARCHIVE set and use this .dll to produce the .efi file that goes into the 
FW image.

This 2 step link process would have the side effect of potentially increasing 
build times, but could be done for specific tool chain families in build_rules.txt.

The first DLINK step could also disable a lot of the optimizations that take 
longer since the goal of this step is only to detect a duplicate symbol.

Best regards,

Mike

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo
> Ersek
> Sent: Thursday, May 25, 2017 1:11 PM
> To: Kinney, Michael D <michael.d.kinney@intel.com>; Ard Biesheuvel
> <ard.biesheuvel@linaro.org>; Andrew Fish (afish@apple.com) <afish@apple.com>
> Cc: Wu, Hao A <hao.a.wu@intel.com>; edk2-devel@lists.01.org; Fan, Jeff
> <jeff.fan@intel.com>
> Subject: Re: [edk2] [Patch] SourceLevelDebugPkg/SecPeiDebugAgentLib: Fix
> duplicate symbol
> 
> On 05/25/17 21:57, Kinney, Michael D wrote:
> > Laszlo,
> >
> > I have the same concern on final image sizes.  I have done some
> > evaluation:
> >
> > GCC5 OVMF X64 DEBUG without -whole-archive
> > ==========================================
> > FV Space Information
> > SECFV [19%Full] 212992 total, 42000 used, 170992 free
> > FVMAIN_COMPACT [33%Full] 3440640 total, 1162760 used, 2277880 free
> > DXEFV [38%Full] 10485760 total, 4024024 used, 6461736 free
> > PEIFV [19%Full] 917504 total, 180648 used, 736856 free
> > Total used = 5409432
> >
> > GCC5 OVMF X64 DEBUG with -whole-archive
> > =======================================
> > FV Space Information
> > SECFV [19%Full] 212992 total, 41936 used, 171056 free
> > FVMAIN_COMPACT [33%Full] 3440640 total, 1158304 used, 2282336 free
> > DXEFV [38%Full] 10485760 total, 4029656 used, 6456104 free
> > PEIFV [19%Full] 917504 total, 181352 used, 736152 free
> > Total used = 5411248
> >
> > Total used difference = 1816 bytes larger with -whole-archive
> >
> > I was also able to do a MSFT VS2015 build with /WHOLEARCHIVE set
> > and it also catches the same duplicate symbol error now.
> >
> > error C2220: warning treated as error - no 'executable' file generated
> > warning C4744: 'mMemoryDiscoveredNotifyList' has different type in
> 'd:\work\github\tianocore\edk2\mdemodulepkg\core\dxeiplpeim\dxeload.c' and
> 'd:\work\github\tianocore\edk2\sourceleveldebugpkg\library\debugagent\secpeidebug
> agent\secpeidebugagentlib.c': 'struct (12 bytes)' and 'array (12 bytes)'
> > DxeIpl.lib(DxeLoad.obj) : error LNK2005: _mMemoryDiscoveredNotifyList already
> defined in SecPeiDebugAgentLib.lib(SecPeiDebugAgentLib.obj)
> >
> d:\work\github\tianocore\edk2\Build\OvmfIa32\DEBUG_VS2015x86\IA32\MdeModulePkg\Co
> re\DxeIplPeim\DxeIpl\DEBUG\DxeIpl.dll : fatal error LNK1169: one or more multiply
> defined symbols found
> >
> > VS2015 OVMF X64 DEBUG without /WHOLEARCHIVE
> > ===========================================
> > FV Space Information
> > SECFV [22%Full] 212992 total, 48560 used, 164432 free
> > FVMAIN_COMPACT [33%Full] 3440640 total, 1147464 used, 2293176 free
> > DXEFV [39%Full] 10485760 total, 4163888 used, 6321872 free
> > PEIFV [22%Full] 917504 total, 204840 used, 712664 free
> > Total used = 5564752
> >
> >
> > VS2015 OVMF X64 DEBUG with /WHOLEARCHIVE
> > ===========================================
> > FV Space Information
> > SECFV [23%Full] 212992 total, 50384 used, 162608 free
> > FVMAIN_COMPACT [33%Full] 3440640 total, 1147424 used, 2293216 free
> > DXEFV [42%Full] 10485760 total, 4422992 used, 6062768 free
> > PEIFV [27%Full] 917504 total, 255528 used, 661976 free
> > Total used = 5875338
> >
> > Total used difference = 310586 bytes larger with /WHOLEARCHIVE
> >
> > For tool chains that do have size impacts, one option is to
> > have a "test" build that enables the linker flags to detect
> > duplicate symbols.  For example the following could be added
> > to a DSC file.  May want to disable GenFds stage when doing
> > this type of build.
> >
> > [BuildOptions]
> > !ifdef $(DETECT_DUPLICATE_SYMBOLS)
> >   MSFT:*_VS2015_*_DLINK_FLAGS = /WHOLEARCHIVE
> > !endif
> 
> Thank you (again) for the research! Looks like the gcc size impact is
> friendly enough to keep --whole-archive enabled at all times (possibly
> due to the --gc-sections flag mentioned by Ard, which we already have
> enabled).
> 
> The VS2015 impact is really large however.
> 
> I was hoping we could add these flags to
> "BaseTools/Conf/tools_def.template", regardless of platform DSC. (If the
> flag is non-default, and/or it's platform-dependent, then it will almost
> never be used, most likely.) But the VS2015 size increase really
> precludes /WHOLEARCHIVE (for the MSFT family) from "tools_def.template".
> 
> Would it be acceptable to add --whole-archive to "tools_def.template"
> only for GCC? After all, at the moment only XCODE*/XCLANG have "-all_load".
> 
> Thanks,
> Laszlo
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