linux - Using CMake to find symbols in libraries -


i trying use cmake find if external library depends on library.

example: hdf5 library can optionally linked zlib in linux, can found with

readelf -ws /usr/local/lib/libhdf5.so | grep inflateend 54: 0000000000000000     0 func    global default  und inflateend

with cmake seems can found checklibraryexists

https://cmake.org/cmake/help/v3.0/module/checklibraryexists.html

in cmake script

set(cmake_required_libraries ${hdf5_library}) check_library_exists(${hdf5_library} inflateend "" need_zlib) message(${need_zlib}) if (need_zlib)  message("-- zlib library needed...") else()  message("-- zlib library not needed...") endif()

output not found

-- looking inflateend in /usr/local/lib/libhdf5.so - not found -- zlib library not needed...

because of did cmake version of using readelf, finds symbol

but, still know why above cmake script fails :-)

the working version is

set(have_read_symbols "no") find_program(read_symbols_prg readelf) if (${read_symbols_prg} matches "readelf")   set(have_read_symbols "yes")   message("-- readelf program found: " ${read_symbols_prg})    execute_process(command ${read_symbols_prg} -ws ${hdf5_library} output_file ${cmake_current_binary_dir}/symbols.txt) endif()  if (${have_read_symbols} matches "yes")   message("-- detecting if hdf5 library ${hdf5_library} needs zlib library...")   file(strings ${cmake_current_binary_dir}/symbols.txt need_zlib regex "inflateend")   if (need_zlib)     message("${color_blue}-- zlib library needed...${color_reset}")   else()     message("-- zlib library not needed...")   endif(need_zlib) endif()

that finds symbol

-- detecting if hdf5 library /usr/local/lib/libhdf5.so needs zlib library... -- zlib library needed...

ok, cmake documentation checklibraryexists() short on details on how accomplished, "check if function exists". checklibraryexists() tries link test program, , depending on success or not, output variable parameter set value 1 or empty.

in case, symbol must 1 defined in libhdf5.so using zlib library. there 1 , 1 symbol case, structure named "h5z_deflate" added library depending on #ifdef zlib case.

so, trick

check_library_exists(${hdf5_library} h5z_deflate "" need_zlib)

however windows case using visual studio error prone, because check_library_exists() detect it, visual studio must set option additional dependencies zlib library, , not requirement library build successfully. so, if option set, check_library_exists detects dependency, if not set, not.


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