libtpetraclassic.so misses dependency information

[nschloe]

When building just Tpetra, e.g., like so

make \
  -DTrilinos_ENABLE_Tpetra:BOOL=ON \
  -DBUILD_SHARED_LIBS:BOOL=ON \
  ../../source-upstream/

everything seems to be going fine. However, the two libraries libtpetraclassic.so and libtpetraclassiclinalg.so come without dependency information:

ldd ./packages/tpetra/classic/src/libtpetraclassic.so
	statically linked

All other libraries seem fine:

ldd ./packages/tpetra/core/src/libtpetra.so
	linux-vdso.so.1 =>  (0x00007fff44bbd000)
	libtrilinos_tpetrakernels.so.12 => /usr/lib/x86_64-linux-gnu/libtrilinos_tpetrakernels.so.12 (0x00007f0ffa397000)
	libtrilinos_tpetraclassicnodeapi.so.12 => /usr/lib/x86_64-linux-gnu/libtrilinos_tpetraclassicnodeapi.so.12 (0x00007f0ffa187000)
	libtrilinos_epetra.so.12 => /usr/lib/x86_64-linux-gnu/libtrilinos_epetra.so.12 (0x00007f0ff9e2d000)
        [...]

I can't quite see what's going wrong yet. Any ideas? @mhoemmen @bartlettroscoe

[mhoemmen]

@nschloe Could you please explain how this affects build correctness? Thanks!

[nschloe]

Well, this means that if you try to link an executable against that library, you'll have to explicitly link all its dependent libraries as well (although you're not directly using them). Typically, you'll find that only some dynamic library link info is missing (and can be detected with -Wl,--no-undefined), but here, something more fishy seems to be going on. The link line for libtpetraclassic.so is

/usr/bin/c++
-fPIC   -pedantic
-Wall -Wno-long-long -Wwrite-strings 
-std=c++11 -O3 -DNDEBUG
-Wl,--no-undefined
-shared
-Wl,-soname,libtpetraclassic.so.12
-o libtpetraclassic.so.12.11 
CMakeFiles/tpetraclassic.dir/Kokkos_Version.cpp.o 
../../../teuchos/kokkoscomm/src/libteuchoskokkoscomm.so.12.11 ../../../teuchos/remainder/src/libteuchosremainder.so.12.11 ../../../teuchos/numerics/src/libteuchosnumerics.so.12.11 ../../../teuchos/comm/src/libteuchoscomm.so.12.11 ../../../teuchos/kokkoscompat/src/libteuchoskokkoscompat.so.12.11 ../../../teuchos/parameterlist/src/libteuchosparameterlist.so.12.11 ../../../teuchos/core/src/libteuchoscore.so.12.11 ../../../kokkos/core/src/libkokkoscore.so.12.11 /usr/lib/x86_64-linux-gnu/libdl.so -lpthread /usr/lib/liblapack.so /usr/lib/libblas.so -Wl,-rpath,/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/kokkoscomm/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/remainder/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/numerics/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/comm/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/kokkoscompat/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/parameterlist/src:/home/nschloe/software/trilinos/build/tpetra/packages/teuchos/core/src:/home/nschloe/software/trilinos/build/tpetra/packages/kokkos/core/src: 

i.e., there's only one object in there: CMakeFiles/tpetraclassic.dir/Kokkos_Version.cpp.o . And guess what: It contains no symbols at all:

nm -D CMakeFiles/tpetraclassic.dir/Kokkos_Version.cpp.o
nm: CMakeFiles/tpetraclassic.dir/Kokkos_Version.cpp.o: no symbols

Indeed, libtpetraclassic.so only contains no interesting symbols:

nm libtpetraclassic.so.12.11 
0000000000201020 B __bss_start
0000000000201020 b completed.7585
                 w __cxa_finalize
00000000000004a0 t deregister_tm_clones
0000000000000530 t __do_global_dtors_aux
0000000000200e78 t __do_global_dtors_aux_fini_array_entry
0000000000201018 d __dso_handle
0000000000200e88 d _DYNAMIC
0000000000201020 D _edata
0000000000201028 B _end
00000000000005a0 T _fini
0000000000000570 t frame_dummy
0000000000200e70 t __frame_dummy_init_array_entry
00000000000005b0 r __FRAME_END__
0000000000201000 d _GLOBAL_OFFSET_TABLE_
                 w __gmon_start__
0000000000000460 T _init
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable
0000000000200e80 d __JCR_END__
0000000000200e80 d __JCR_LIST__
                 w _Jv_RegisterClasses
00000000000004e0 t register_tm_clones
0000000000201020 d __TMC_END__

That can't be right, can it?

[tawiesn]

It's my understanding that TpetraClassic is a placeholder, that we need for backwards compatibility, during the transition to the new Tpetra stack (which is rather complete?). Looking at the TpetraClassic code your observations are not surprising. I guess, TpetraClassic will go away at some point.
@mhoemmen Can you comment on this?

[mhoemmen]

@tawiesn wrote:

It's my understanding that TpetraClassic is a placeholder, that we need for backwards compatibility, during the transition to the new Tpetra stack (which is rather complete?). Looking at the TpetraClassic code your observations are not surprising. I guess, TpetraClassic will go away at some point.

That's correct. It doesn't have any meaningful contents, except perhaps for an enum definition and some headers that remain for backwards compatibility. It will go away at some point.

[nschloe]

Alright, I guess the Debian warnings are safe to ignore. Thanks for the explanation!