Code coverage in clang - c

Question

I'm trying to generate code coverage files for a small C program compiled with clang on Debian Linux. Here's what I've done:
neuron#debian:~/temp$ ls
main.c test.c test.h
neuron#debian:~/temp$ clang *.c
neuron#debian:~/temp$ ./a.out
0
This is exactly as expected, I can compile and run things. Now trying to enable coverage.
neuron#debian:~/temp$ clang --coverage *.c
/usr/bin/ld: cannot find /usr/bin/../lib/libprofile_rt.a: No such file or directory
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Trying to include the library for linking.
neuron#debian:~/temp$ clang --coverage -lprofile_rt *.c
/usr/bin/ld: cannot find -lprofile_rt
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Finding the library:
neuron#debian:~/temp$ find / -name \*profile_rt\* 2>/dev/null
/usr/lib/llvm-3.0/lib/libprofile_rt.so
/usr/lib/llvm-3.0/lib/libprofile_rt.a
neuron#debian:~/temp$ clang --coverage -lprofile_rt -L/usr/lib/llvm-3.0/lib *.c
/usr/bin/ld: cannot find /usr/bin/../lib/libprofile_rt.a: No such file or directory
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Here's more verbose output of the last command: http://pastie.org/8468331. What concerns me there:
the linker uses tons of gcc libraries to link with (though this may be a result of llvm not having it's own binunitls);
profiling library is being searched for at /usr/bin/../lib/libprofile_rt.a instead of the path I provided.
If we pass the arguments to the linker the output is the same:
neuron#debian:~/temp$ clang --coverage -Wl,-L/usr/lib/llvm-3.0/lib *.c -lprofile_rt
/usr/bin/ld: cannot find /usr/bin/../lib/libprofile_rt.a: No such file or directory
clang: error: linker command failed with exit code 1 (use -v to see invocation)
What do I do wrong?

Answer 1

Try changing the order of your link line from
clang --coverage -lprofile_rt -L/usr/lib/llvm-3.0/lib *.c
to
clang --coverage -L/usr/lib/llvm-3.0/lib *.c -lprofile_rt
Ok, doesn't seem like the linker is getting your -L for some reason. Maybe try
clang --coverage -Wl,L/usr/lib/llvm-3.0/lib *.c -lprofile_rt

Answer 2

The only way I've been able to resolve this issue is by creating a symbolic link to where LLVM/clang is looking for the library. I'm thinking this is a way for package maintainers to manage which feature-library is used by the host system.
ln -s /usr/lib/llvm-3.0/lib/libprofile_rt.a /usr/lib/libprofile_rt.a
Coverage, and other optional -f<***> profile features work as expected. I can verify this by adding the verbose -v switch.
Debian clang version 3.0-6.2 (tags/RELEASE_30/final) (based on LLVM 3.0)
Target: arm-unknown-linux-gnueabihf
Thread model: posix
"/usr/bin/clang" -cc1 -triple armv4t-unknown-linux-gnueabihf -S -disable-free -disable-llvm-verifier -main-file-name example.c -mrelocation-model static -mdisable-fp-elim -mconstructor-aliases -target-abi apcs-gnu -target-cpu arm1136jf-s -mfloat-abi hard -target-linker-version 2.22 -momit-leaf-frame-pointer -v -femit-coverage-notes -femit-coverage-data -resource-dir /usr/bin/../lib/clang/3.0 -fmodule-cache-path /var/tmp/clang-module-cache -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib/clang/3.0/include -internal-externc-isystem /usr/include/arm-linux-gnueabihf -internal-externc-isystem /usr/include -ferror-limit 19 -fmessage-length 130 -fno-signed-char -fgnu-runtime -fobjc-runtime-has-arc -fobjc-runtime-has-weak -fobjc-fragile-abi -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/example-lLKOP1.s -x c example.c
clang -cc1 version 3.0 based upon llvm 3.0 hosted on arm-unknown-linux-gnueabihf
ignoring nonexistent directory "/usr/bin/../lib/clang/3.0/include"
ignoring nonexistent directory "/usr/bin/../lib/clang/3.0/include"
ignoring duplicate directory "/usr/local/include"
ignoring duplicate directory "/usr/include/arm-linux-gnueabihf"
ignoring duplicate directory "/usr/include/arm-linux-gnueabihf"
ignoring duplicate directory "/usr/include/arm-linux-gnueabihf"
ignoring duplicate directory "/usr/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/include/arm-linux-gnueabihf
/usr/include
/usr/include/clang/3.0/include/
/usr/lib/gcc/arm-linux-gnueabihf/4.6/include/
/usr/lib/gcc/arm-linux-gnueabihf/4.6/include-fixed/
End of search list.
"/usr/bin/as" -o /tmp/example-WbJHFT.o /tmp/example-lLKOP1.s
"/usr/bin/ld" -X --hash-style=both --build-id --eh-frame-hdr -m armelf_linux_eabi -dynamic-linker /lib/ld-linux-armhf.so.3 -o example.o /usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o /usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crti.o /usr/lib/gcc/arm-linux-gnueabihf/4.6/crtbegin.o -L/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf -L/lib/arm-linux-gnueabihf -L/usr/lib/arm-linux-gnueabihf -L/usr/lib/gcc/arm-linux-gnueabihf/4.6 -L/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf -L/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../.. -L/lib/arm-linux-gnueabihf -L/lib -L/usr/lib/arm-linux-gnueabihf -L/usr/lib /tmp/example-WbJHFT.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed \
/usr/lib/gcc/arm-linux-gnueabihf/4.6/crtend.o \
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crtn.o \
/usr/bin/../lib/libprofile_rt.a