On Fri, Dec 3, 2010 at 11:10 AM, Cary Coutant <ccout...@google.com> wrote: >>>> Another way to do this would be to put a marker in the command line >>>> that identifies where those libraries begin, and the linker could just >>>> go back and rescan those libraries if needed, before the final layout >>>> of the endcaps. >>> >>> I like that idea in general, but the difficulty is knowing where to put >>> the marker. E.g., the user is going to specify -lm, and we are going to >>> need to rescan it. If the user writes -lm -lmylib1 -lmylib2 we want to >>> rescan -lm but we don't really need to rescan mylib1 and mylib2. >> >> All those complexities make 2 stage linking more attractive. I >> think I can implement it in GNU linker with the current plugin API. >> >> Linker just needs to remember the command line options, including >> >> --start-group/--end-group >> -as-needed/--no-as-needed >> --copy-dt-needed-entries/--no-copy-dt-needed-entries >> >> in stage 1. >> >> In stage 2, it will place LTO trans files before the first IR file >> claimed by plugin and process the command line options. >> >> --whole-archive may need some special handling. Archives >> after --whole-archive will be ignored in stage 2. > > It seems to me that we just need to add a few more libraries as > pass-through libraries, being careful to add a pass-through option > only for libraries that are already on the command line. How does that > add up to "all those complexities"? > > With what you've written here, you've just added to the complexity of > your proposed solution, which makes it a much bigger change -- > especially since what you're proposing will require changes in both > linkers. Adding pass-through options is a gcc driver change only. >
I will implement 2 stage linking in GNU linker with the current plugin API. The change shouldn't be too big. pass-through isn't needed. If we keep it in GCC driver, my linker will simply ignore it. One benefit is everything will just work, with or without LTO. -- H.J.
