[Openmp-dev] CMAKE_INSTALL_PREFIX vs -fopenmp and clang search library search path

[Jack Howarth]

On Wed, May 13, 2015 at 11:58 AM, Chandler Carruth <chandlerc at google.com> wrote:
> I think that openmp should work much more like libc++ than like the
> sanitizers. It has a reasonably stable API and even supports the libgomp
> APIs and so it should be in the normal library tree just like libc++.
>

Chandler,
       Is linux able to find the installed libc++ shared library when
-DCMAKE_INSTALL_PREFIX=
is used in the cmake build? On x86_64 darwin, the built libc++ shared
library is installed
in the lib subdirectory of the path from CMAKE_INSTALL_PREFIX.
However, this isn't really
exercised on darwin as the system libc++ is always used by default.

> However, the CMake build of the openmp needs a lot of work. =/ It doesn't
> match the patterns and structures of any of our other runtime libraries.

Please do open bugzilla reports on those issues against the openmp cmake build.
             Jack

>
> I think openmp needs to much more closely model its CMake build on libc++'s
> before we do anything more. Currently I can't even reasonably include it in
> my builds because it clobbers un-prefixed variable names and doesn't re-use
> any of the LLVM CMake logic.
>
> Also, I'll point out that the CMake build completely and universally uses
> the term 'iomp'. This trend really needs to reverse....
>
> On Wed, May 13, 2015 at 8:32 AM Jack Howarth
> <howarth.mailing.lists at gmail.com> wrote:
>>
>>     I believe we have a gap in clang's library search path with the
>> enabling of the openmp support via the proposed patch at...
>>
>>
>> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150511/129075.html
>>
>> Currently, in tree cmake builds of the openmp library using
>> -DCMAKE_INSTALL_PREFIX to install the llvm build in a buried
>> subdirectory will place the libiomp5.dylib shared library in a
>> directory outside of the library search path used by clang...
>>
>> % clang-3.7 -fopenmp -o omp_getEnvInfo omp_getEnvInfo.c -v
>> clang version 3.7.0 (trunk)
>> Target: x86_64-apple-darwin14.4.0
>> Thread model: posix
>>  "/sw/opt/llvm-3.7.0/bin/clang-3.7" -cc1 -triple
>> x86_64-apple-macosx10.10.0 -emit-obj -mrelax-all -disable-free
>> -disable-llvm-verifier -main-file-name omp_getEnvInfo.c
>> -mrelocation-model pic -pic-level 2 -mthread-model posix
>> -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2
>> -target-linker-version 242 -v -dwarf-column-info
>> -fno-unique-section-names -resource-dir
>> /sw/opt/llvm-3.7.0/bin/../lib/clang/3.7.0 -fdebug-compilation-dir
>> /Users/howarth/openmp_examples -ferror-limit 19 -fmessage-length 140
>> -fopenmp -stack-protector 1 -mstackrealign -fblocks
>> -fobjc-runtime=macosx-10.10.0 -fencode-extended-block-signature
>> -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o
>> /var/folders/1l/n78sywl52lz6kkys6nv7mnph0000gp/T/omp_getEnvInfo-e20595.o
>> -x c omp_getEnvInfo.c
>> clang -cc1 version 3.7.0 based upon LLVM 3.7.0svn default target
>> x86_64-apple-darwin14.4.0
>> ignoring nonexistent directory "/usr/local/include"
>> #include "..." search starts here:
>> #include <...> search starts here:
>>  /sw/opt/llvm-3.7.0/bin/../lib/clang/3.7.0/include
>>  /usr/include
>>  /System/Library/Frameworks (framework directory)
>>  /Library/Frameworks (framework directory)
>> End of search list.
>>  "/sw/opt/llvm-3.7.0/bin/ld" -demangle -dynamic -arch x86_64
>> -macosx_version_min 10.10.0 -o omp_getEnvInfo -liomp5
>> /var/folders/1l/n78sywl52lz6kkys6nv7mnph0000gp/T/omp_getEnvInfo-e20595.o
>> -lSystem
>> ld: library not found for -liomp5
>> clang-3.7: error: linker command failed with exit code 1 (use -v to
>> see invocation)
>>
>> requiring an explicit path to passed to the compiler...
>>
>> % clang-3.7 -fopenmp -L/sw/opt/llvm-3.7.0/lib -o omp_getEnvInfo
>> omp_getEnvInfo.c
>> % otool -L ./omp_getEnvInfo
>> ./omp_getEnvInfo:
>> /sw/opt/llvm-3.7.0/lib/libiomp5.dylib (compatibility version 5.0.0,
>> current version 5.0.0)
>> /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current
>> version 1213.0.0)
>>
>> Currently, all the other shared libraries linked by the clang
>> compilers (aside from libc++) are expected to be located in the
>> clang/3.7.0/lib/darwin subdirectory (such as
>> libclang_rt.asan_iossim_dynamic.dylib and
>> libclang_rt.asan_osx_dynamic.dylib). Using CMAKE_INSTALL_PREFIX in the
>> cmake build to bury the llvm installation has no impact on the usage
>> of those two libraries with the -fsanitize flags but the current
>> search library search path doesn't do the same for the libiomp5
>> relocation in the same case.
>>             Jack
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