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I have a script that builds llvm/clang 3.42 from source (with configure+make). It runs smooth on ubuntu 14.04.5 LTS. When I upgraded to ubuntu 17.04, the build fails.

Here is the building script:

svn co https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_342/final llvm svn co https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_342/final llvm/tools/clang svn co https://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_342/final llvm/projects/compiler-rt svn co https://llvm.org/svn/llvm-project/libcxx/tags/RELEASE_342/final llvm/projects/libcxx rm -rf llvm/.svn rm -rf llvm/tools/clang/.svn rm -rf llvm/projects/compiler-rt/.svn rm -rf llvm/projects/libcxx/.svn cd llvm ./configure \ --enable-optimized \ --disable-assertions \ --enable-targets=host \ --with-python="/usr/bin/python2" make -j `nproc`

Here are the errors I get (TLDR: problems with definitions of malloc, calloc, realloc and free)

/usr/include/malloc.h:38:14: error: declaration conflicts with target of using declaration already in scope extern void *malloc (size_t __size) __THROW __attribute_malloc__ __wur; ^ /usr/include/stdlib.h:427:14: note: target of using declaration extern void *malloc (size_t __size) __THROW __attribute_malloc__ __wur; ^ /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3./stdlib.h:65:12: note: using declaration using std::malloc; ^ In file included from /home/oren/GIT/LatestKlee/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc:47: /usr/include/malloc.h:41:14: error: declaration conflicts with target of using declaration already in scope extern void *calloc (size_t __nmemb, size_t __size) ^ /usr/include/stdlib.h:429:14: note: target of using declaration extern void *calloc (size_t __nmemb, size_t __size) ^ /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/stdlib.h:59:12: note: using declaration using std::calloc; ^ In file included from /home/oren/GIT/LatestKlee/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc:47: /usr/include/malloc.h:49:14: error: declaration conflicts with target of using declaration already in scope extern void *realloc (void *__ptr, size_t __size) ^ /usr/include/stdlib.h:441:14: note: target of using declaration extern void *realloc (void *__ptr, size_t __size) ^ /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/stdlib.h:73:12: note: using declaration using std::realloc; ^ In file included from /home/oren/GIT/LatestKlee/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc:47: /usr/include/malloc.h:53:13: error: declaration conflicts with target of using declaration already in scope extern void free (void *__ptr) __THROW; ^ /usr/include/stdlib.h:444:13: note: target of using declaration extern void free (void *__ptr) __THROW; ^ /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/stdlib.h:61:12: note: using declaration using std::free; ^ COMPILE: clang_linux/tsan-x86_64/x86_64: /home/oren/GIT/LatestKlee/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cc 4 errors generated. Makefile:267: recipe for target '/home/oren/GIT/LatestKlee/llvm/tools/clang/runtime/compiler-rt/clang_linux/tsan-x86_64/x86_64/SubDir.lib__tsan__rtl/tsan_platform_linux.o' failed make[5]: *** [/home/oren/GIT/LatestKlee/llvm/tools/clang/runtime/compiler-rt/clang_linux/tsan-x86_64/x86_64/SubDir.lib__tsan__rtl/tsan_platform_linux.o] Error 1

The default gcc version shipped with ubuntu 17.04 is 6.3. Maybe this is an issue of default C++ dialect used by gcc 6.3? Any help is very much appreciated, thanks!

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2 Answers 2

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That seems to be an issue with LLVM 3.4.2tsan (Thread Sanitizer) failing to build with GCC 6.x, as previously reported here:

https://aur.archlinux.org/packages/clang34-analyzer-split

It seems the inclusion of stdlib.h and malloc.h is conflicting, since both define malloc and friends.

It's possible that this issue only manifets in tsan, so if tsan is not instrumental to your LLVM build (which is very likely), and you wish to stick with the system gcc for building LLVM, you may consider disabling tsan completely.

If you're running a CMake build (as in here), you can do so by commenting line 29 of llvm/projects/compiler-rt/lib/CMakeLists.txt:

if (CMAKE_SYSTEM_NAME MATCHES "Linux" AND NOT ANDROID) add_subdirectory(tsan) # comment out this line

If you're forced to stick to the configure build, my best guess would be removing the tsan-x86_64 target in llvm/projects/compiler-rt/make/clang_linux.mk, line 63:

Configs += full-x86_64 profile-x86_64 san-x86_64 asan-x86_64 --> tsan-x86_64 <--
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many thanks for all the effort, I indeed do not need tsan, and when disabling everything works fine.
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I faced the same problem on my Ubuntu 16.10. It has default gcc 6.2. You need to instruct LLVM build system to use gcc 4.9. Also, I suggest you remove GCC6 completely.

$ sudo apt-get remove g++-6 gcc-6 cpp $ sudo apt-get install gcc-4.9 g++4.9 $ export CC=/usr/bin/gcc-4.9 $ export CXX=/usr/bin/g++-4.9 $ export CPP=/usr/bin/cpp-4.9 $ ./configure $ make

And maybe you will need:

$ sudo ln -s /usr/bin/cpp-4.9 /usr/bin/cpp
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Note that there's probably no need to remove the installed gcc - different versions could happily live together. You could toggle between them using update-alternatives --config gcc or just specify the version number as you suggest, such as gcc-4.9. Generally removing system gcc is not advisable.
Also, it's important to install multilib as well: sudo apt-get install gcc-4.9 g++4.9 g++-4.9-multilib Or you may end up with a partial and broken gcc installtion.
Thanks Alexander and @valiano, but it seems I can't even install gcc-4.9 on Ubuntu 17.04 for some reason ... I have posted that separately in SO: stackoverflow.com/questions/48398475/… ...

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