On 25 May 2017 at 11:06, Laszlo Ersek <[email protected]> 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. >> Visual Studio 2015 Update 2 has also added a new linker flag called >> /WHOLEARCHIVE. I am working on evaluating that flag to see if it >> catches the same issue. > > Thanks! > Laszlo > >>> -----Original Message----- >>> From: Laszlo Ersek [mailto:[email protected]] >>> Sent: Thursday, May 25, 2017 9:09 AM >>> To: Kinney, Michael D <[email protected]>; Ard Biesheuvel >>> <[email protected]>; Andrew Fish ([email protected]) <[email protected]> >>> Cc: Wu, Hao A <[email protected]>; [email protected]; Fan, Jeff >>> <[email protected]> >>> Subject: Re: [edk2] [Patch] SourceLevelDebugPkg/SecPeiDebugAgentLib: Fix >>> duplicate >>> symbol >>> >>> 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. >>> >>> 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 >>> >>>> -all_load >>>> Loads all members of static archive libraries. This option does >>>> not apply to dynamic shared libraries. >>> >>> >>> Thanks >>> Laszlo > _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
