[Re-sending this to try to got through to the GCC mailing list... Sorry for the duplication to others... My reply is at the bottom]
On Mon, Jun 18, 2012 at 11:08 AM, Chandler Carruth <chandl...@google.com> wrote: > On Mon, Jun 18, 2012 at 10:49 AM, Rafael Espíndola > <rafael.espind...@gmail.com> wrote: >> >> > The GNU linker has support to merge .ctor's into init_array. Does the >> > gold linker have the same feature? This seems more like the real fix >> > rather than just hacking around the issue. >> >> Recent version have it. I found the bug when using gold 2.21 which >> doesn't. What seems to happen is: >> >> * In an old linux system, the linker leaves ctors in .ctors, >> crtbeginS.o has a call to __do_global_dtors_aux. The net result is >> that _init calls the constructors. >> * In an all new linux system, the compiler uses .init_array (or the >> linker moves it there) and crtbeginS.o has nothing to do with >> constructors. >> * If we have a compiler that doesn't use .init_array and gold 2.21 in >> a new linux system, we hit the bug. >> >> So this is not as bad as I was expecting (old programs still work), >> but it is still a somewhat annoying ABI change to handle. > > > Thanks to Andrew for explaining some of this to Rafael, and thanks to Rafael > for breaking it down and getting it through my thick skull. =] I now > understand what's going on much better. It is indeed not as bad as I was > expecting. > > However, as Rafael says, this is an annoying ABI change to handle. It seems > that the song-and-dance to maintain backwards compatibility has been > achieved, but the cost has been to introduce a pretty nasty dependency on > newer versions of ld / gold in order to cope with '.o' files built by old > compilers (which we are sometimes stuck with). > > In figuring out how best to support this situation, the question I'm left > with, and would love if someone from the GCC community familiar with the > initial change could answer is: why was this change worth the cost we're now > paying? What is the expected upside to putting constructors in .init_array? > > Thanks, > -Chandler
