[bug] linker can't find downloaded libraries

[NoSpooksAllowed]

Hello, I just tried to build test example from getting started page in conan, but for some reason linker does not see downloaded libraries, even that according to conan they were downloaded

Environment Details (include every applicable attribute)

• Operating System+version: Ubuntu 20.10
• Compiler+version: g++ 10.2.0
• Conan version: 1.33.0
• Python version: 3.8.6

Steps to reproduce (Include if Applicable)

Just exact same steps from this example https://docs.conan.io/en/latest/getting_started.html

Logs (Executed commands with output) (Include/Attach if Applicable)

user@user:~/Documents/cpp/conan-test/build$ cmake --build .
gmake[1]: Entering directory '/home/user/Documents/cpp/conan-test/build'
gmake[2]: Entering directory '/home/user/Documents/cpp/conan-test/build'
Scanning dependencies of target md5
gmake[2]: Leaving directory '/home/user/Documents/cpp/conan-test/build'
gmake[2]: Entering directory '/home/user/Documents/cpp/conan-test/build'
[ 50%] Building CXX object CMakeFiles/md5.dir/md5.cpp.o
[100%] Linking CXX executable bin/md5
/usr/bin/ld: CMakeFiles/md5.dir/md5.cpp.o: in function main': md5.cpp:(.text.startup+0xb5): undefined reference to Poco::DigestEngine::digestToHex[abi:cxx11](std::vector<unsigned char, std::allocator > const&)'
collect2: error: ld returned 1 exit status
gmake[2]: *** [CMakeFiles/md5.dir/build.make:84: bin/md5] Error 1
gmake[2]: Leaving directory '/home/user111/Documents/cpp/conan-test/build'
gmake[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/md5.dir/all] Error 2
gmake[1]: Leaving directory '/home/user111/Documents/cpp/conan-test/build'
gmake: *** [Makefile:84: all] Error 2

[solvingj]

Can you post the generated conanbuildinfo.cmake file?

Also, can you post the section from your CMakeLists.txt where you do include() on it, just to confirm you're including it correctly?

[NoSpooksAllowed]

conanbuildinfo.cmake

https://pastebin.com/bYNAK3DL

CMakeLists.txt

https://pastebin.com/TqXh2N7L

[solvingj]

Everything looks good in these files.

Line 43 of conanbuildinfo.cmake is here:

set(CONAN_LIB_DIRS_POCO "/home/user111/.conan/data/poco/1.9.4/_/_/package/05430cbc4154f78d465015e2e36dc71b2d92c2d8/lib")

Line 49 is here:

set(CONAN_LIBS_POCO PocoZip PocoNetSSL PocoDataSQLite PocoRedis PocoUtil PocoMongoDB PocoXML PocoCrypto PocoEncodings PocoNet PocoData PocoJSON PocoFoundation)

So, in theory, there should be a PocoCrypto library file (.a or .so) in the lib directory shown. Lets verify that.

Then, there's this line from CMakeLists.txt:

target_link_libraries(md5 ${CONAN_LIBS})

In theory, Cmake should be generating a Makefile with the corresponding path and passing it to the linker with -l ...

It would be helpful to see the actual linker command or the flags. You can tell CMake and make to be more verbose using this CMake variable (and then re-running your cmake command):
https://cmake.org/cmake/help/latest/variable/CMAKE_VERBOSE_MAKEFILE.html

Alternatively, you can just look into the CMakeFiles directory for flags.make which makes it very easy to find exactly what flags will be sent to the compiler and linker.

We need to figure out where the ball is being dropped exactly.

[NoSpooksAllowed]

Well, I checked a folder, and all these libraries in there.

Here is more verbose output:

https://pastebin.com/5VQYZqt7

[solvingj]

Ok, so now we have it narrowed to this line:

/usr/bin/c++         -rdynamic CMakeFiles/md5.dir/md5.cpp.o  -o bin/md5   -L/home/user111/.conan/data/poco/1.9.4/_/_/package/05430cbc4154f78d465015e2e36dc71b2d92c2d8/lib  -L/home/user111/.conan/data/pcre/8.41/_/_/package/d7ce5e9581d2c53c1703b35527fc2b00e0fc00f8/lib  -L/home/user111/.conan/data/expat/2.2.10/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib  -L/home/user111/.conan/data/sqlite3/3.33.0/_/_/package/0afebc877508f94e1a69d4ab9e6230d79a6ac293/lib  -L/home/user111/.conan/data/openssl/1.1.1h/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib  -L/home/user111/.conan/data/bzip2/1.0.8/_/_/package/91a8b22c2c5a149bc617cfc06cdd21bf23b12567/lib  -L/home/user111/.conan/data/zlib/1.2.11/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib  -Wl,-rpath,/home/user111/.conan/data/poco/1.9.4/_/_/package/05430cbc4154f78d465015e2e36dc71b2d92c2d8/lib:/home/user111/.conan/data/pcre/8.41/_/_/package/d7ce5e9581d2c53c1703b35527fc2b00e0fc00f8/lib:/home/user111/.conan/data/expat/2.2.10/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib:/home/user111/.conan/data/sqlite3/3.33.0/_/_/package/0afebc877508f94e1a69d4ab9e6230d79a6ac293/lib:/home/user111/.conan/data/openssl/1.1.1h/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib:/home/user111/.conan/data/bzip2/1.0.8/_/_/package/91a8b22c2c5a149bc617cfc06cdd21bf23b12567/lib:/home/user111/.conan/data/zlib/1.2.11/_/_/package/19729b9559f3ae196cad45cb2b97468ccb75dcd1/lib -lPocoNetSSL -lPocoZip -lPocoUtil -lPocoMongoDB -lPocoDataSQLite -lPocoRedis -lPocoCrypto -lPocoEncodings -lPocoNet -lPocoJSON -lPocoXML -lPocoData -lPocoFoundation -lpcreposix -lpcre -lpcre16 -lpcre32 -lexpat -lsqlite3 -lssl -lcrypto -lbz2 -lz -lrt -ldl -lpthread 

/usr/bin/ld: CMakeFiles/md5.dir/md5.cpp.o: in function `main':
md5.cpp:(.text+0x9d): undefined reference to `Poco::DigestEngine::digestToHex[abi:cxx11](std::vector<unsigned char, std::allocator<unsigned char> > const&)'

[solvingj]

Seems this is duplicate issue:

conan-io/examples#40

It seems you need to add this line to your profile:

compiler.libcxx=libstdc++11

Quote from @memsharded regarding the background:

Conan by default uses compiler.libcxx=libstdc++ for wider compatibility in all distros and gcc versions
If you are running a modern distro and gcc >= 5 you need to change it to libstdc++11
But if you are running an older distro (even with gcc >= 5) or gcc < 5, then you need to keep the libstdc++

[NoSpooksAllowed]

It's working now. Thank you so much!