OpenMP MacOS -ld上的错误:在体系结构x86_64中找不到符号

Question

我已经在我的macos中安装了OpenMP和xcode-选择。

$ clang-omp --version
clang version 3.5.0
Target: x86_64-apple-darwin15.4.0
Thread model: posix

$ xcode-select --version
xcode-select version 2343.

同时运行以下非常简单的代码

  1 #include <omp.h>                                                                                                                                                              
  2 #include <stdio.h>                                                                                  
  3                                                                                                     
  4 #define n 20                                                                                        
  5                                                                                                     
  6 int main(){                                                                                         
  7                                                                                                     
  8 int i;                                                                                              
  9 int tid;                                                                                            
 10                                                                                                     
 11 omp_set_num_threads(3);                                                                             
 12 #pragma omp parallel for private(tid) schedule(static,1)                                            
 13                                                                                                     
 14 for (i=0; i<n; i++) {                                                                               
 15  tid = omp_get_thread_num();                                                                        
 16  printf("Thread %d executing iteration %d\n", tid, i);                                              
 17 }                                                                                                   
 18 }     

我搞错了

$ clang-omp -openmp parallel.c -v

clang version 3.5.0 
Target: x86_64-apple-darwin15.4.0
Thread model: posix
 "/usr/local/Cellar/clang-omp/2015-04-01/libexec/bin/clang-3.5" -cc1 -triple x86_64-apple-macosx10.11.0 -emit-obj -mrelax-all -disable-free -main-file-name parallel.c -mrelocation-model pic -pic-level 2 -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -v -dwarf-column-info -resource-dir /usr/local/Cellar/clang-omp/2015-04-01/libexec/bin/../lib/clang/3.5.0 -fdebug-compilation-dir /Users/prayagupd/prayag.data/workspace.programming/parallel-programming/openMP -ferror-limit 19 -fmessage-length 178 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.11.0 -fencode-extended-block-signature -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/63/jvvb4wy16gx6w76mkgsvn52m0000gn/T/parallel-32b98e.o -x c parallel.c
clang -cc1 version 3.5.0 based upon LLVM 3.5.0svn default target x86_64-apple-darwin15.4.0
ignoring nonexistent directory "/usr/local/Cellar/clang-omp/2015-04-01/libexec/usr/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/local/Cellar/clang-omp/2015-04-01/libexec/bin/../lib/clang/3.5.0/include
 /usr/local/opt/libiomp/include/libiomp
 /usr/local/Cellar/clang-omp/2015-04-01/libexec/include/c++/v1
 /usr/include
 /System/Library/Frameworks (framework directory)
 /Library/Frameworks (framework directory)
End of search list.
 "/usr/bin/ld" -dynamic -arch x86_64 -macosx_version_min 10.11.0 -o penmp /var/folders/63/jvvb4wy16gx6w76mkgsvn52m0000gn/T/parallel-32b98e.o -lSystem
Undefined symbols for architecture x86_64:
  "_omp_get_thread_num", referenced from:
      _main in parallel-32b98e.o
  "_omp_set_num_threads", referenced from:
      _main in parallel-32b98e.o
ld: symbol(s) not found for architecture x86_64
clang-3.5: error: linker command failed with exit code 1 (use -v to see invocation)

gcc连omp.h都找不到。

$ gcc parallel.c -fopenmp -o parallel
parallel.c:1:10: fatal error: 'omp.h' file not found
#include <omp.h>
         ^
1 error generated.

gcc版本

$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
Target: x86_64-apple-darwin15.4.0
Thread model: posix

Answer 1

对于clang-omp问题，您导出库路径了吗？ala

export DYLD_LIBRARY_PATH=(OMPLIB PATH):$DYLD_LIBRARY_PATH

也许你没有安装英特尔的OpenMP库？现代的clang(>3.7)，没有随OS一起打包，现在支持开箱即用OpenMP。

对于你的gcc问题，OS实际上并没有提供gcc，它只是将其链接到香草的clang。因此，您正在尝试用不支持OpenMP的编译器编译它。如果你想要gcc，那么安装它通过端口或自制。