Build glibc for sh4-unknown-linux-gnu currently fails if one's
using GCC5/6: in dl-conflict.c, the elf_machine_rela() function
is called with NULL as its 3rd argument, sym. The implementation
of that function in sysdeps/sh/dl-machine.h dereferences that pointer:
const Elf32_Sym *const refsym = sym;
...
if (map == &GL(dl_rtld_map))
value -= map->l_addr + refsym->st_value + reloc->r_addend;
GCC discovers a null pointer dereference, and in accordance with
-fdelete-null-pointer-checks (which is enabled in -O2) replaces this
code with a trap - which, as SH does not implement a trap pattern in
GCC, evaluates to an abort() call. This abort() call pulls many more
objects from libc_nonshared.a, eventually resulting in link failure
due to multiple definitions for a number of symbols.
As far as I see, the conditional before this code is always false in
rtld: _dl_resolve_conflicts() is called with main_map as the first
argument, not GL(_dl_rtld_map), but since that call is in yet another
compilation unit, GCC does not know about it. Patch that wraps this
conditional into !defined RESOLVE_CONFLICT_FIND_MAP attached.
* sysdeps/sh/dl-machine.h (elf_machine_rela): The condition
in R_SH_DIR32 case is always false when inlined from
dl-conflict.c. Ifdef out to prevent GCC from insertin an
abort() call.
d40dbe722f