[cfe-dev] Can't compile simple OpenMP code with clang 5.0.0 (original) (raw)

Johannes Doerfert via cfe-dev cfe-dev at lists.llvm.org
Tue Dec 22 13:49:56 PST 2020

Hi Marcus,

On 12/22/20 2:57 PM, Marcus Johnson via cfe-dev wrote:

Another thing:

Clang can be compiled without OpenMP support, which removes the omp.h header, libomp.dylib, and tablegen isn’t even run for OpenMP pragmas. Your Clang distribution needs to be compiled with OpenMP support for it to work at all.

As far as I can tell, LLVM/Clang doesn't have the ability to disable OpenMP support. This might have been different in the past, or in some derived compilers, but I would assume the clang would have emitted an error upon encountering -fopenmp then.

~ Johannes

On Dec 22, 2020, at 12:55 PM, Marcus Johnson <MarcusLJohnson1991 at gmail.com> wrote:

Why are you using such an old version of Clang? Clang the compiler needs to be built with support for parsing OpenMP pragmas. It’s not just the header and runtime you need to successfully compile with OpenMP On Dec 22, 2020, at 11:57 AM, Керим Хемраев via cfe-dev <cfe-dev at lists.llvm.org> wrote:

Hi, I’m struggling with compiling simple OpenMP program with clang 5.0.0. Here is the code (foo.cxx): #include "omp.h" #include <stdio.h> int main(void) { #pragma omp parallel printf("thread %d\n", ompgetthreadnum()); } As I use clang as part of xeus-cling my clang installation is inside conda packages: $ which clang /home/tasik/miniconda3/envs/cling/bin/clang As this clang package does’t have omp.h I provide additional directories to find omp.h and libomp.so To compile the code I use the command: $ clang -fopenmp -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib foo.cxx And I get errors: /usr/bin/ld: cannot find /lib64/libpthread.so.0 /usr/bin/ld: cannot find /usr/lib64/libpthreadnonshared.a clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation) I really need some help to undertand how to work with clang 5.0.0 OpenMP And I think that it is difficult to update clang’s version as xeus-cling requires mentioned 5.0.0 version... With respect, kerim

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