Created attachment 24435 [details]
Minimal example

I have a library which needs to be compiled as PIC (amd64). It has different parts which cannot be written in C and thus uses inline assembly. Other parts can benefit extremely by using LTO (~10% faster and ~10% size reduction). By default it is compiled using something like that:


$ gcc -g -O2 -fPIC -DPIC -o test.o -c test.c
$ gcc -fPIC -shared test.o -o test.so

This works perfectly. It will produce an PIC error when compiling it with LTO:


$ gcc -flto -g -O2 -fPIC -DPIC -o test.o -c test.c
$ gcc -flto -g -O2 -fPIC -DPIC -shared test.o -o test.so
/usr/bin/ld: /tmp/ccMYQCew.ltrans0.ltrans.o: relocation R_X86_64_PC32 against undefined symbol `evil_long' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status


To the version I use:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.0-11' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-multiarch --with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc --with-arch-32=i586 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 20110604 (prerelease) (Debian 4.6.0-11) 
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/collect2 --build-id --no-add-needed --eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1 -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../.. --version -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crtn.o
collect2 version 4.6.1 20110604 (prerelease) (x86-64 Linux/ELF)
/usr/bin/ld --build-id --no-add-needed --eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1 -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../.. --version -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/crtn.o
GNU ld (GNU Binutils for Debian) 2.21.51.20110523
Copyright 2011 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty