[cfe-dev] Problem linking in some dataflow sanitizer functions?
Peter Collingbourne
peter at pcc.me.uk
Wed Jan 14 13:14:52 PST 2015
Hi Christian,
Are you sure that you have checked out libcxx and libcxxabi into llvm/projects
(i.e. alongside compiler-rt)? Once you have done so, it may be necessary
to run CMake again to pick up the new projects (the safest thing to do is
probably to delete the llvm-build-dfsan directory and redo step 2).
Peter
On Wed, Jan 14, 2015 at 04:05:49PM -0500, Christian Convey wrote:
> 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
>
--
Peter
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