This is the mail archive of the mailing list for the binutils project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: PATCH: 2 stage BFD linker for LTO plugin

On Tue, Jan 18, 2011 at 4:27 PM, Ian Lance Taylor <> wrote:
> After some discussion on IRC, here is another approach to resolving the
> issue with static linking and LTO.
> In this approach, the linker keeps track of all archives found after the
> first file claimed by the plugin. ?If the plugin adds any object files,
> and the object files refer to any symbols which are not yet defined,
> then the linker will scan all the saved archives, in order, for a
> definition of the symbol. ?If a definition is found, the linker will
> pull in the appropriate object from the archive. ?If that object, in
> turn, has any undefined symbols, the linker will pull in the appropriate
> object from that archive or any later ones, and so forth. ?The linker
> will honor --start-group/--end-group while rescanning.
> This should ensure that any previously unseen undefined symbols
> introduced by the compiler are handled correctly. ?I think it is
> appropriate to do this unconditionally when using plugins, as there is
> no other reasonable way to handle undefined symbols in a file added by a
> plugin.
> I've appended a patch to gold which implements this approach. ?The patch
> is reasonably efficient and introduces no unnecessary file I/O. ?With
> this patch to gold, and no change to gcc, the problematic -static test
> cases which I know about pass. ?Also all the current lto.exp tests pass.
> All those tests also pass if I edit the gcc LTO plugin to ignore the
> -pass-through option, as that option is not necessary when the linker
> implements this approach.

I think -pass-through is a hack and linker should simply ignore it.

> As this patch does not require any changes to gcc, and fixes some cases
> which are clearly bugs, I plan to commit this patch to binutils mainline
> and to binutils 2.21 branch after a few days if I don't hear any
> comments.

It sounds a real progress.

BTW, can you check if the modified gold works on

	PR ld/12248
	PR ld/12277
	PR ld/12291
	PR ld/12323
	PR ld/12365
	PR ld/12369



Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]