Boost::iostream fails at linking stage missing bz2 library

[NeroBurner]

The current Boost 1.88.0 with Boost-config.cmake file has a problem with the Boost::iostream example, as it fails at linking stage missing bz2 library

[ 50%] Building CXX object CMakeFiles/foo.dir/foo.cpp.o
/usr/bin/clang++ -DBOOST_IOSTREAMS_NO_LIB -DBOOST_SERIALIZATION_NO_LIB -isystem /builds/hunter/hunter/_Base/xxxxxxx/ae89ed9/bfa4c80/Install/include -std=c++17 -fPIE -MD -MT CMakeFiles/foo.dir/foo.cpp.o -MF CMakeFiles/foo.dir/foo.cpp.o.d -o CMakeFiles/foo.dir/foo.cpp.o -c /builds/hunter/hunter/examples/Boost-iostreams/foo.cpp
[100%] Linking CXX executable foo
/usr/bin/cmake -E cmake_link_script CMakeFiles/foo.dir/link.txt --verbose=1
/usr/bin/clang++ CMakeFiles/foo.dir/foo.cpp.o -o foo  /builds/hunter/hunter/_Base/xxxxxxx/ae89ed9/bfa4c80/Install/lib/libboost_iostreams-mt-d-x64.a /builds/hunter/hunter/_Base/xxxxxxx/ae89ed9/bfa4c80/Install/lib/libboost_serialization-mt-d-x64.a /builds/hunter/hunter/_Base/xxxxxxx/ae89ed9/bfa4c80/Install/lib/libzd.a /builds/hunter/hunter/_Base/xxxxxxx/ae89ed9/bfa4c80/Install/lib/libbz2d.a -lbz2 -lz -lbz2 -lz
/usr/bin/ld: cannot find -lbz2
/usr/bin/ld: cannot find -lbz2
clang: error: linker command failed with exit code 1 (use -v to see invocation)

It seems to be an upstream issue: boostorg/iostreams#177

for some unclear reason the bz2 library is not found while linking even tough the library is present in the hunter lib folder.

[TheNetos]

I can confirm that it is reproduced already in Boost version 1.83, after switching to hunter v0.26.1.

Maybe this is what influenced it.

By directly disabling the use of bz2 in the configuration, everything builds successfully:

hunter_config(Boost VERSION 1.83.0
    CMAKE_ARGS
        IOSTREAMS_NO_BZIP2=1
        ...
)

[NeroBurner]

yes definitely the change we use Boosts cmake config file now.

thanks for the workaround! do you think we should make that a default for now? maybe with an open issue to check if the next boost version fixes it?

[TheNetos]

do you think we should make that a default for now? maybe with an open issue to check if the next boost version fixes it?

I don't think this is a problem in Boost.

According to their source, dependencies are looked for like this:

function(boost_iostreams_option name description package version found target) # sources...

  find_package(${package} ${version} QUIET)

  if(${found} AND TARGET ${target})

    option(${name} ${description} ON)

  else()

    option(${name} ${description} OFF)

  endif()

  if(${name})

    find_package(${package} ${version} REQUIRED)
    target_sources(boost_iostreams PRIVATE ${ARGN})
    target_link_libraries(boost_iostreams PRIVATE ${target})

  endif()

endfunction()

boost_iostreams_option(BOOST_IOSTREAMS_ENABLE_ZLIB "Boost.Iostreams: Enable ZLIB support" ZLIB "" ZLIB_FOUND ZLIB::ZLIB src/zlib.cpp src/gzip.cpp)
boost_iostreams_option(BOOST_IOSTREAMS_ENABLE_BZIP2 "Boost.Iostreams: Enable BZip2 support" BZip2 "" BZIP2_FOUND BZip2::BZip2 src/bzip2.cpp)
boost_iostreams_option(BOOST_IOSTREAMS_ENABLE_LZMA "Boost.Iostreams: Enable LZMA support" LibLZMA "" LIBLZMA_FOUND LibLZMA::LibLZMA src/lzma.cpp)
boost_iostreams_option(BOOST_IOSTREAMS_ENABLE_ZSTD "Boost.Iostreams: Enable Zstd support" zstd "1.0" zstd_FOUND zstd::libzstd_shared src/zstd.cpp)

The issue here seems to be at the intersection between issuing dependencies from hunter and requesting dependencies in Boost.

I'll investigate the potential causes and write here.