[cfe-dev] Problem linking in some dataflow sanitizer functions?

[Peter Collingbourne]

Hi Christian,

There was a bug that prevented clients from using the dfsan_get_label_info
function. That bug is now fixed in compiler-rt r225692.

Peter

On Mon, Jan 12, 2015 at 12:56:01PM -0500, Christian Convey wrote:
> Hello, I'm using the dataflow sanitizer in clang 3.6 for the first
> time, I'm I'm running into some linker errors.  I was wondering if
> someone could point out my mistake?
> 
> I downloaded (today) from git the current llvm, clang, and compiler-rt
> code.  It built without any problem.
> 
> Using that build of clang/llvm, I'm able to run the example code shown
> here:  http://clang.llvm.org/docs/DataFlowSanitizer.html#example
> 
> However, I have a linking problem when I try to extend the example.
> When I try to call the function "dfsan_get_label_info", the linker
> can't find it.  This is a bit of a surprise, because it does appear to
> be defined in my LLVM build:
> 
> cconvey at spaceman /tmp $ nm
> /home/cconvey/dw/clang-llvm-git/build/bin/../lib/clang/3.6.0/lib/linux/libclang_rt.dfsan-x86_64.a
> | grep dfsan_get_label_info
> 0000000000000990 T _Z20dfsan_get_label_infot
> cconvey at spaceman /tmp $ c++filt _Z20dfsan_get_label_infot
> dfsan_get_label_info(unsigned short)
> 
> And I'm reasonably sure I'm linking in that .a file:
> 
> cconvey at spaceman /tmp $
> /home/cconvey/dw/clang-llvm-git/build/bin/clang  -fsanitize=dataflow
> foo.c -v
> clang version 3.6.0 (http://llvm.org/git/clang.git
> 48d2f2367001a51a3253cc34aea4a91c92fd45fb)
> (http://llvm.org/git/llvm.git
> ad017096fc8eec5afd256f572d8d0b9d5d8aa09f)
> ...
> End of search list.
>  "/usr/bin/ld" -pie --eh-frame-hdr -m elf_x86_64 -dynamic-linker
> /lib64/ld-linux-x86-64.so.2 -o a.out
> /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/Scrt1.o
> /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crti.o
> /usr/lib/gcc/x86_64-linux-gnu/4.8/crtbeginS.o
> -L/usr/lib/gcc/x86_64-linux-gnu/4.8
> -L/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu
> -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
> -L/usr/lib/gcc/x86_64-linux-gnu/4.8/../../..
> -L/home/cconvey/dw/clang-llvm-git/build/bin/../lib -L/lib -L/usr/lib
> -whole-archive /home/cconvey/dw/clang-llvm-git/build/bin/../lib/clang/3.6.0/lib/linux/libclang_rt.dfsan-x86_64.a
> -no-whole-archive
> --dynamic-list=/home/cconvey/dw/clang-llvm-git/build/bin/../lib/clang/3.6.0/lib/linux/libclang_rt.dfsan-x86_64.a.syms
> /tmp/foo-5310a2.o --no-as-needed -lpthread -lrt -lm -ldl -lgcc
> --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s
> --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.8/crtendS.o
> /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crtn.o
> /tmp/foo-5310a2.o: In function `dfs$execute_tree':
> foo.c:(.text+0xa89): undefined reference to `dfsan_get_label_info'
> /tmp/foo-5310a2.o: In function `dfsw$dfsan_get_label_info':
> foo.c:(.text.dfsw$dfsan_get_label_info[dfsw$dfsan_get_label_info]+0xb):
> undefined reference to `dfsan_get_label_info'
> clang-3.6: error: linker command failed with exit code 1 (use -v to
> see invocation)
> cconvey at spaceman /tmp $
> 
> (I'm also having linkage problems when my code uses C++ iostreams, but
> I figured I'd work through this issue first.)
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-- 
Peter