At this line:

It's not immediately obvious to me how to fix the bug. Does sharedstructures rely on having pointers offset by 1 byte?

Having trouble building on Arch Linux.

$ make
[  3%] Building CXX object CMakeFiles/sharedstructures.dir/src/Allocator.cc.o
In file included from /tmp/sharedstructures/src/Allocator.hh:5,
                 from /tmp/sharedstructures/src/Allocator.cc:1:
/tmp/sharedstructures/src/Pool.hh:191:27: error: ignoring packed attribute because of unpacked non-POD field ‘std::atomic<long unsigned int> sharedstructures::Pool::Data::size’ [-Werror]
  191 |     std::atomic<uint64_t> size;
      |                           ^~~~
In file included from /tmp/sharedstructures/src/Allocator.hh:6:
/tmp/sharedstructures/src/ProcessLock.hh:11:24: error: ignoring packed attribute because of unpacked non-POD field ‘std::atomic<int> sharedstructures::ProcessLock::lock’ [-Werror]
   11 |   std::atomic<int32_t> lock;
      |                        ^~~~
/tmp/sharedstructures/src/ProcessLock.hh:18:24: error: ignoring packed attribute because of unpacked non-POD field ‘std::atomic<int> sharedstructures::ProcessReadWriteLock::write_lock’ [-Werror]
   18 |   std::atomic<int32_t> write_lock;
      |                        ^~~~~~~~~~
/tmp/sharedstructures/src/ProcessLock.hh:19:24: error: ignoring packed attribute because of unpacked non-POD field ‘std::atomic<int> sharedstructures::ProcessReadWriteLock::reader_tokens [65]’ [-Werror]
   19 |   std::atomic<int32_t> reader_tokens[NUM_READER_SLOTS];
      |                        ^~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
make[2]: *** [CMakeFiles/sharedstructures.dir/build.make:76: CMakeFiles/sharedstructures.dir/src/Allocator.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:103: CMakeFiles/sharedstructures.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

I've attached the output of my cmake .. (too big to paste in)
sharedstructures_cmake.txt

Hi Guys,

I'm using Ubuntu 20.04, but python cannot find the module (ModuleNotFoundError: No module named 'sharedstructures') and neither can I on my OS.

I get the messages from cmake:
-- Building Python module
-- FIND_PACKAGE_MESSAGE_DETAILS_Python3=[/usr/bin/python3.9][/usr/lib/x86_64-linux-gnu/libpython3.9.so][/usr/include/python3.9][cfound components: Interpreter Development ][v3.9.5()]

Thanks for a hint!

I get the compliation errror:

/usr/bin/ld: /usr/local/lib/libsharedstructures.a(LogarithmicAllocator.cc.o): in function sharedstructures::LogarithmicAllocator::verify() const':
/home/ilja/sharedstructures/src/LogarithmicAllocator.cc:514: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /home/ilja/sharedstructures/src/LogarithmicAllocator.cc:519: undefined reference to string_printf[abi:cxx11](char const*, ...)'
/usr/bin/ld: /home/ilja/sharedstructures/src/LogarithmicAllocator.cc:523: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /home/ilja/sharedstructures/src/LogarithmicAllocator.cc:531: undefined reference to string_printf[abi:cxx11](char const*, ...)'
/usr/bin/ld: /home/ilja/sharedstructures/src/LogarithmicAllocator.cc:540: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(LogarithmicAllocator.cc.o):/home/ilja/sharedstructures/src/LogarithmicAllocator.cc:545: more undefined references to string_printf[abi:cxx11](char const*, ...)' follow
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::open_segment(char const*, int, unsigned int, bool)': /home/ilja/sharedstructures/src/Pool.cc:20: undefined reference to shm_open'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::unlink_segment(char const*, bool)': /home/ilja/sharedstructures/src/Pool.cc:28: undefined reference to shm_unlink'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::Pool(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long, bool)': /home/ilja/sharedstructures/src/Pool.cc:34: undefined reference to scoped_fd::scoped_fd()'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:45: undefined reference to scoped_fd::operator=(int)' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:46: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:47: undefined reference to scoped_fd::operator=(int)' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:48: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:49: undefined reference to cannot_open_file::cannot_open_file(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:53: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:53: undefined reference to fstat(int)' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:59: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:69: undefined reference to scoped_fd::operator int() const' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:72: undefined reference to string_for_errorabi:cxx11'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:75: undefined reference to scoped_fd::operator int() const' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:34: undefined reference to scoped_fd::~scoped_fd()'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::~Pool()': /home/ilja/sharedstructures/src/Pool.cc:86: undefined reference to scoped_fd::~scoped_fd()'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::expand(unsigned long)': /home/ilja/sharedstructures/src/Pool.cc:108: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:109: undefined reference to string_for_error[abi:cxx11](int)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::check_size_and_remap() const':
/home/ilja/sharedstructures/src/Pool.cc:120: undefined reference to scoped_fd::operator int() const' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:120: undefined reference to fstat(int)'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:126: undefined reference to scoped_fd::operator int() const' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:129: undefined reference to string_for_errorabi:cxx11'
/usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:130: undefined reference to scoped_fd::operator int() const' /usr/bin/ld: /home/ilja/sharedstructures/src/Pool.cc:131: undefined reference to string_printf[abi:cxx11](char const*, ...)'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::map_and_call(unsigned long, unsigned long, std::function<void (void*, unsigned long)>)': /home/ilja/sharedstructures/src/Pool.cc:148: undefined reference to scoped_fd::operator int() const'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(Pool.cc.o): in function sharedstructures::Pool::delete_pool(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bool)': /home/ilja/sharedstructures/src/Pool.cc:166: undefined reference to string_for_errorabi:cxx11'
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(PrefixTree.cc.o): in function sharedstructures::PrefixTree::LookupResult::str[abi:cxx11]() const': /home/ilja/sharedstructures/src/PrefixTree.cc:107: undefined reference to string_printf[abi:cxx11](char const*, ...)'
/usr/bin/ld: /home/ilja/sharedstructures/src/PrefixTree.cc:109: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /home/ilja/sharedstructures/src/PrefixTree.cc:111: undefined reference to string_printf[abi:cxx11](char const*, ...)'
/usr/bin/ld: /home/ilja/sharedstructures/src/PrefixTree.cc:113: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(PrefixTree.cc.o): in function sharedstructures::PrefixTree::get_structure_for_contents[abi:cxx11](unsigned long) const':
/home/ilja/sharedstructures/src/PrefixTree.cc:1447: undefined reference to string_printf[abi:cxx11](char const*, ...)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(PrefixTree.cc.o):/home/ilja/sharedstructures/src/PrefixTree.cc:1456: more undefined references to string_printf[abi:cxx11](char const*, ...)' follow
/usr/bin/ld: /usr/local/lib/libsharedstructures.a(ProcessLock.cc.o): in function sharedstructures::this_process_token()': /home/ilja/sharedstructures/src/ProcessLock.cc:63: undefined reference to getpid_cached()'
/usr/bin/ld: /usr[ 3%] Built target sensor_msgs_generate_messages_eus
/local/lib/libsharedstructures.a(ProcessLock.cc.o): in function sharedstructures::process_for_token_is_running(int)': /home/ilja/sharedstructures/src/ProcessLock.cc:89: undefined reference to pid_exists(int)'
/usr/bin/ld: /home/ilja/sharedstructures/src/ProcessLock.cc:92: undefined reference to pid_is_zombie(int)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(ProcessLock.cc.o): in function sharedstructures::futex_wait(std::atomic, int, timespec const)':
/home/ilja/sharedstructures/src/ProcessLock.cc:115: undefined reference to string_for_error[abi:cxx11](int)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(ProcessLock.cc.o): in function sharedstructures::futex_wake(std::atomic, int)':
/home/ilja/sharedstructures/src/ProcessLock.cc:122: undefined reference to string_for_error[abi:cxx11](int)' /usr/bin/ld: /usr/local/lib/libsharedstructures.a(ProcessLock.cc.o): in function sharedstructures::wait_for_reader_drain(sharedstructures::ProcessReadWriteLock, bool)':
/home/ilja/sharedstructures/src/ProcessLock.cc:242: undefined reference to getpid_cached()' collect2: error: ld returned 1 exit status make[2]: *** [01_gpr/mmcl_cpp_particle_weight/CMakeFiles/example_sharedmemory_node.dir/build.make:107: /home/ilja/01_lobabo_ego_ws/ros1/devel/lib/mmcl_cpp_particle_weight/example_sharedmemory_node] Error 1 make[1]: *** [CMakeFiles/Makefile2:7672: 01_gpr/mmcl_cpp_particle_weight/CMakeFiles/example_sharedmemory_node.dir/all] Error 2

Question

How do I solve this :)

In cmakelists I do actually everything right:

find_library(ARRAY_LIBRARY sharedstructures PATHS /usr/lib /usr/local/lib)

include_directories(
include
${catkin_INCLUDE_DIRS}
${Boost_INCLUDE_DIRS}
/home/ilja/sharedstructures/src
/home/ilja/sharedstructures
)

target_link_libraries(example_sharedmemory_node
${catkin_LIBRARIES}
${Boost_FILESYSTEM_LIBRARY}
${Boost_SYSTEM_LIBRARY}
${Boost_REGEX_LIBRARY}
${RT_LIBRARY}
/usr/local/lib/libsharedstructures.a
${ARRAY_LIBRARY}
)

Maybe you can gfive me a hint, because this lib is perfectly suited for my problem. Thanks a lot.