https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85492
--- Comment #3 from Jim Wilson <wilson at gcc dot gnu.org> --- I figured out that I wasn't fully rebuilding and relinking all libraries while trying to debug this with printf, and that sent me down the wrong path. Trying this again, correctly, I see that we have a loop in unwind, because the return address for _start is pointing at _start. This works by accident when static linking, because crt1.o is included before crtbegin.o, crtbegin.o registers FDEs starting from a label it adds to the eh_frame section, and hence the FDE for _start in crt1.o gets lost. When unwinding, we see that there is no FDE for _start, and it isn't an exception frame, so that terminates unwinding. When dynamic linking, we use PT_GNU_EH_FRAME which uses eh_frame section addresses and hence finds every FDE, including the one for _start, so we try to unwind through _start, get a return address pointing at _start, and go into an infinite loop. This requires a glibc patch to fix. Just setting the return address in _start to 0 works.
