[Bug c++/65199] New: Linker failure with -flto

[goswin-v-b at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65199

            Bug ID: 65199
           Summary: Linker failure with -flto
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: goswin-v-b at web dot de
              Host: x86_64-linux-gnu
            Target: x86_64-linux-gnu
             Build: arm-none-eabi

I'm building a bare-metal kernel for a Raspberry Pi 2 (armv7) in c++. At some
point this failed with "undefined reference to `memcpy'" so I implemented one
as extern "C" void * memcpy(void *dest, const void *src, uint32_t n). But that
gives a different error:

% arm-none-eabi-g++ -O2 -W -Wall -fPIE -flto -march=armv7-a -mfloat-abi=hard
-mfpu=vfpv3-d16 -ffreestanding -nostdlib -std=gnu++11 -fno-exceptions -fno-rtti
-c -o main.o main.cc
% arm-none-eabi-g++ -fPIE -nostdlib -O2 -flto boot.o font.o main.o -lgcc
-Tlink-arm-eabi.ld -o kernel.elf
`memcpy' referenced in section `.text' of /tmp/cc7IkgU6.ltrans0.ltrans.o:
defined in discarded section `.text' of main.o (symbol from plugin)
collect2: error: ld returned 1 exit status

Running the same command to link but without -flto succeeds:

% arm-none-eabi-g++ -fPIE -nostdlib -O2 boot.o font.o main.o -lgcc
-Tlink-arm-eabi.ld -o kernel.elf