On Thu, Dec 2, 2010 at 1:10 PM, Cary Coutant <ccout...@google.com> wrote: >> I propose that we add a new linker option: --plugin-callback. At each >> point where this option appears on the command line, the linker will >> call a new plugin callback entry point. The LTO plugin will replace the >> all_symbols_read callback with this one. We will have the gcc driver >> run the linker more or less like this: >> >> object-files -lc -lgcc --plugin-callback -lc -lgcc crtend.o crtn.o > > I'm not sure how this is any better than the pass-through option we're > already using. That just has the plugin re-inject those libraries that > you have placed after the --plugin-callback option. The crtend.o and > crtn.o files could be handled by having the plugin claim them and > re-inject them at the end. > > For every new routine that the gcc backend generates a new call to, it > ought to know which library that routine is defined in, and should be > able to add that library after the generated object(s) during the > all-symbols-read callback. We really don't want to support arbitrary > interposition at that point, because a user-supplied replacement might > invalidate some assumptions that were made during optimization. >
It sounds reasonable. We have to add those libraries very carefully. For example, with "gcc -static" on Linux, the reference to glibc should be passed to linker as "--start-group -lgcc -lgcc_eh -lc --end-group". -- H.J.
