[Bug lto/78795] New: LTO causes undefined reference errors when linking with GMP "make check"

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78795

            Bug ID: 78795
           Summary: LTO causes undefined reference errors when linking
                    with GMP "make check"
           Product: gcc
           Version: 6.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincent-gcc at vinc17 dot net
  Target Milestone: ---

With GCC 4.9.4 and 6.2.1 under GNU/Linux (Debian/sid), when I build GMP 6.1.1
with

--disable-shared CFLAGS="-march=native -O3 -flto=jobserve -fuse-linker-plugin"

then "make check", I get errors like:

/tmp/ccw6C9Xr.ltrans0.ltrans.o: In function `main':
<artificial>:(.text.startup+0xb): undefined reference to `tests_start'
<artificial>:(.text.startup+0x11): undefined reference to `mp_trace_base'
<artificial>:(.text.startup+0x35): undefined reference to `__gmpn_random'
<artificial>:(.text.startup+0x3f): undefined reference to `ref_bswap_limb'
<artificial>:(.text.startup+0x74): undefined reference to `mpn_trace'
<artificial>:(.text.startup+0x88): undefined reference to `mpn_trace'
<artificial>:(.text.startup+0x9c): undefined reference to `mpn_trace'
<artificial>:(.text.startup+0xa6): undefined reference to `tests_end'
collect2: error: ld returned 1 exit status

These errors are similar to those from bug 69953, but with 2 differences: bug
69953 is about C++ (compiled with g++, vs gcc here) and it is known to work
with GCC 4.9.2.