TL;DR The problem appears to be related to binutils and not clang.
I am having the same problem as the submitter with Clang 3.5.0-9. Compiling the following simple hello world program: #include <iostream> int main() { std::cout << "Hello World\n"; return 0; } $ clang++ -flto -c hello.cpp $ clang++ -v -flto hello.o -o hello Debian clang version 3.5.0-9 (tags/RELEASE_350/final) (based on LLVM 3.5.0) Target: x86_64-pc-linux-gnu Thread model: posix Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.8 Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.8.4 Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.9 Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.9.2 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7.4 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.4 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9 Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.2 Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.8 Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.8.4 Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.9 Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.9.2 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9 Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2 Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9 Candidate multilib: .;@m64 Selected multilib: .;@m64 "/usr/bin/ld" --hash-style=both --build-id --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o hello /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/crtbegin.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/4.9 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../.. -L/usr/lib/llvm-3.5/bin/../lib -L/lib -L/usr/lib -plugin /usr/lib/llvm-3.5/bin/../lib/LLVMgold.so -plugin-opt=mcpu=x86-64 hello.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/crtend.o /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crtn.o hello.o: file not recognized: File format not recognized clang: error: linker command failed with exit code 1 (use -v to see invocation) It appears that the default linker is not the gold linker. $ ls -l /usr/bin/ld* lrwxrwxrwx 1 root root 6 Dec 25 16:33 /usr/bin/ld -> ld.bfd -rwxr-xr-x 1 root root 1076192 Dec 19 13:30 /usr/bin/ld.bfd -rwxr-xr-x 1 root root 5388 Nov 6 15:12 /usr/bin/ldd -rwxr-xr-x 1 root root 2642264 Dec 19 13:30 /usr/bin/ld.gold The following workaround fixed the problem for me. $ sudo rm /usr/bin/ld $ sudo ln -s ld.gold /usr/bin/ld $ clang++ -flto hello.o -o hello $ ./hello Hello World Perhaps this bug should be reassigned to binutils. $ dpkg -S /usr/bin/ld binutils: /usr/bin/ld $ dpkg -S /usr/bin/ld.gold binutils: /usr/bin/ld.gold -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org