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

[Christian Convey]

Hi Peter,

Sorry for the slow reply.  I tried to following your instructions
precisely (since I think that was one of your main points), and I ran
into trouble on the "ninja" invocation:

cconvey at spaceman ~/dw/clang-llvm-git/llvm-build-dfsan $ ninja cxx cxxabi
ninja: error: unknown target 'cxx', did you mean 'lli'?

Please let me know if you'd like me to try something else.

Cheers,
Christian

On Mon, Jan 12, 2015 at 5:10 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
> Hi Christian,
>
> If you wish to compile C++ programs with DFSan, you will first need to
> compile the C++ standard library with DFSan. Unfortunately, the way to do
> this is quite painful at the moment, and needs to be simplified and documented
> better. This way worked for me:
>
> 1. Check out the libcxx and libcxxabi projects into the LLVM projects directory.
>
> 2. Use cmake to configure a separate build directory in which to build libcxx
>    and libcxxabi with DFSan:
>
>     # assuming that your LLVM source directory is ~/src/llvm and build directory is ~/src/llvm-build
>     mkdir ~/src/llvm-build-dfsan
>     cd ~/src/llvm-build-dfsan
>     CC=~/src/llvm-build/bin/clang CXX=~/src/llvm-build/bin/clang++ cmake -G Ninja ../llvm -DCMAKE_C_FLAGS=-fsanitize=dataflow -DCMAKE_CXX_FLAGS=-fsanitize=dataflow -DLIBCXXABI_ENABLE_SHARED=NO -DLIBCXX_ENABLE_SHARED=NO -DLLVM_FORCE_USE_OLD_TOOLCHAIN=YES -DLIBCXX_CXX_ABI=libcxxabi
>
> 3. Build only libc++ and libc++abi in the just-configured build directory:
>     ninja cxx cxxabi
>
> 3. To compile your program, pass the following flags to clang++:
>
>    compile flags: -stdlib=libc++ -fsanitize=dataflow -I$HOME/src/llvm-build-dfsan/include/c++/v1
>    link flags: -stdlib=libc++ -fsanitize=dataflow -L$HOME/src/llvm-build-dfsan/lib -Wl,--start-group,-lc++abi
>
> I was able to compile and run your hello world program this way. Please let
> me know if it works for you.
>
> Thanks,
> Peter
>
> On Mon, Jan 12, 2015 at 04:25:48PM -0500, Christian Convey wrote:
>> Thanks Peter.  That seems to have done the trick for dfsan_get_label_info.
>>
>> I'm still having trouble with C++ STL functions, though.  Any idea why
>> I might be getting the following?
>>
>> I have this simple test program, foo2.c:
>> >>>>>
>> #include <iostream>
>>
>> using namespace std;
>>
>> int main(void) {
>>     cout << "Hellow, world!" << endl;
>>     return 0;
>> }
>> <<<<<
>>
>> When I build it without the dataflow sanitizer, things work fine:
>> /home/cconvey/dw/clang-llvm-git/build/bin/clang++ -std=c++11  foo2.cpp
>>
>> However, when I enable the sanitizer, there are a lot of unmet
>> dependencies.  Any idea if I'm doing something wrong on the command
>> line?
>> cconvey at spaceman /tmp $
>> /home/cconvey/dw/clang-llvm-git/build/bin/clang++ -std=c++11
>> -fsanitize=dataflow foo2.cpp
>> /tmp/foo2-8b9f0f.o: In function `main':
>> foo2.cpp:(.text+0xb): undefined reference to
>> `dfs$_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_'
>> foo2.cpp:(.text+0x44): undefined reference to
>> `dfs$_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc'
>> foo2.cpp:(.text+0x6a): undefined reference to `dfs$_ZNSolsEPFRSoS_E'
>> /tmp/foo2-8b9f0f.o: In function `dfs$__cxx_global_var_init':
>> foo2.cpp:(.text.startup+0x1d): undefined reference to
>> `dfs$_ZNSt8ios_base4InitC1Ev'
>> foo2.cpp:(.text.startup+0x24): undefined reference to
>> `dfs$_ZNSt8ios_base4InitD1Ev'
>> clang-3.6: error: linker command failed with exit code 1 (use -v to
>> see invocation)
>>
>>
>> Thanks,
>> Christian
>>
>> On Mon, Jan 12, 2015 at 3:43 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
>> > 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.)
>> >> _______________________________________________
>> >> cfe-dev mailing list
>> >> cfe-dev at cs.uiuc.edu
>> >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>> >>
>> >
>> > --
>> > Peter
>>
>
> --
> Peter