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Tip_Cmake_gcc.md

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building shared libs

  • CMAKE_SHARED_LINKER_FLAGS="-Wl,-Bsymbolic" when links are messed up

enforcing $PREFIX/lib64

  • Ubuntu may make $PREFIX/lib
  • CMAKE_INSTALL_LIBDIR:PATH=lib64

local/global text symbol

  • or just local/global symbol
  • For library files like
$ nm libvtkCommonDataModel-9.1.so
.... T _Zn17vtkXMLData ...
.... U _Z.....
.... t _Z....
  • T means global symbol
  • U means undefined (wouldbe defined in other library file)
  • t means local symbol

compiling VTK with -DModule_vktCommonCore=ON -DModule_vtkCommonDataModel=ON

  • gcc8.4 yields library with T, global symbol but gcc10.3 yielded with t, local
  • Now linker with other source code yields undefined reference message
  • How to enforce T, not t, in the library?
    • In Cmake files, add_library(someLib SHARED IMPORTED GLOBAL) will enforce global symbol -> but not working?
    • Comparing CMakeCache.txt by gcc8.4 vs 10.3, COMPILER_HAS_DEPRECATED:INTERNAL=1 is found at gcc8.4. 10.3 has no value.
    • ~~Needs newer version of cmake? This is 3.20.5
    • Tried vtk 9.1 and worked OK. But this will need the higher version of CMake (> 3.12)

setting system variable within cmake

  • In ExternalProject_Add ()
    • CONFIGURE_COMMAND ${CMAKE_COMMAND} -E env TMPDIR=/tmp mkdir myfolder && cmake --prefix=/opt/myapps

intel2021 + mvapich2 on AMD cpu

  • Hangs at FindMPI()
    • Check through cmake --trace-expand
    • ROI: execute_process(mpicxx -showme:compile ...)
      • Actually this was not the cause. The real issue was that MPI_CXX_WORKS failed (FALSE found. Must be TRUE)
      • Failing from mpicxx -mkl=sequential test_mpi.cpp
  • Intel cpu seems OK
  • Found at 3.11, 3.28, 3.29, ...
  • Alternative solution
    • Instead of mpicxx, use icpc and provide -DCMAKE_CXX_FLAGS="..."
    • The contents can be found from mpicxx -show
    • Might not work on building external projects
  • The cause was the failure of try_compile(...) at FindMPI.cmake
    • Test test_mpi.c from FindMPI folder
    • MKL library was not found from linking
    • Added -DCMAKE_CXX_FLAGS="-L${MKLROOT}/lib/intel64" resolved the isue

Order of external project build

  • Adding dependencies on external projects
ExternalProject_Add(
    AAA_PROJECT
    ...
)
ExternalProject_Add(
    BBB_PROJECT
    DEPENDS AAA_PROJECT
    ...
)

Avoid rebuilding external project

  • At ExternalProject_Add()
  • Ref: https://stackoverflow.com/questions/56986726/cmake-externalproject-add-rebuilds-every-time
  • Use UPDATE_COMMAND ""
  • ? May not work
  • If the location of external project is determined by CMAKE_BINARY_DIR, CMakeCache.txt of the external packages might be re-written when a new build is requested
    • CMakeCache.txt is re-written, recompiling all source codes
    • Use CMAKE_SOURCE_DIR instead
    • When old CMakeCache.txt survives, compilation will skip as Make command will compile any changed code only
  • Once built, recompiling source package will not rebuild external packages
    • If external packages need recompiling - due to any source code change - then use BUILD_ALWAYS 1
      • This will compile any changed code only - not building from scratch