why is linking to libOpenCL.dylib failing with undefined symbol

I am trying to build the pocl library on MacOS

System:

MBP 16" 2019
Intel i9, AMD Radeon 5500m
Mac OS 12.4
using bash, instead of zsh
llvm from home-brew, -version 14

I have the following in my .bash_profile to setup the build environment

export PATH=/usr/local/opt/llvm/bin:$PATH
export CC=clang
export CMAKE_C_COMPILER=clang
export CXX=clang++
export CMAKE_CXX_COMPILER=clang++

I go and clone the repo with git, cd into the source directory, mkdir build

Then in build/ run:

cmake .. -DENABLE_TESTS=OFF -DENABLE_EXAMPLES=OFF -DENABLE_ICD=OFF

The config seems to work and then when I run make everything builds, and gets to the end but then gives me the following error:

[100%] Linking C executable poclcc
clang-14: warning: argument unused during compilation: '-pie' [-Wunused-command-line-argument]
Undefined symbols for architecture x86_64:
  "_clBuildProgram", referenced from:
      _main in poclcc.c.o
      _poclu_load_program_multidev in libpoclu.a(misc.c.o)
  "_clCreateCommandQueue", referenced from:
      _poclu_get_any_device2 in libpoclu.a(misc.c.o)
      _poclu_get_multiple_devices in libpoclu.a(misc.c.o)
  "_clCreateContext", referenced from:
      _main in poclcc.c.o
      _poclu_get_any_device2 in libpoclu.a(misc.c.o)
      _poclu_get_multiple_devices in libpoclu.a(misc.c.o)
  "_clCreateContextFromType", referenced from:
      _poclu_create_any_context in libpoclu.a(misc.c.o)
  "_clCreateProgramWithBinary", referenced from:
      _poclu_load_program_multidev in libpoclu.a(misc.c.o)
  "_clCreateProgramWithIL", referenced from:
      _poclu_load_program_multidev in libpoclu.a(misc.c.o)
  "_clCreateProgramWithSource", referenced from:
      _main in poclcc.c.o
      _poclu_load_program_multidev in libpoclu.a(misc.c.o)
  "_clGetDeviceIDs", referenced from:
      _main in poclcc.c.o
      _poclu_get_any_device2 in libpoclu.a(misc.c.o)
      _poclu_get_multiple_devices in libpoclu.a(misc.c.o)
  "_clGetDeviceInfo", referenced from:
      _main in poclcc.c.o
      _poclu_load_program_multidev in libpoclu.a(misc.c.o)
  "_clGetPlatformIDs", referenced from:
      _main in poclcc.c.o
      _poclu_create_any_context in libpoclu.a(misc.c.o)
      _poclu_get_any_device2 in libpoclu.a(misc.c.o)
      _poclu_get_multiple_devices in libpoclu.a(misc.c.o)
  "_clGetProgramBuildInfo", referenced from:
      _main in poclcc.c.o
      _poclu_show_program_build_log in libpoclu.a(misc.c.o)
  "_clGetProgramInfo", referenced from:
      _main in poclcc.c.o
      _poclu_show_program_build_log in libpoclu.a(misc.c.o)
  "_clReleaseContext", referenced from:
      _main in poclcc.c.o
  "_clReleaseProgram", referenced from:
      _main in poclcc.c.o
ld: symbol(s) not found for architecture x86_64

I checked and libOpenCL.dylib was successfully built in the pocl/build/lib/CL/ directory. Just as a check, I tried compiling clinfo with a direct link to this library and it gave me the same set of error messages shown above.

Running nm libOpenCL.dylib | grep clBuildProgram prints the following:

0000000000013850 t _clBuildProgram

So its in there, but it is a local text section symbol. I don't actually know what that means though, and if that means it should work, or should not work. I don't actually understand what the problem is here or why this linking is failing, or what to do about it. Looking for some guidance on that.

Solution

The meaning of the lower case t is that the symbols are local, i.e. not externally visible to linking programs. Upper case T would be externally visible.

POCL has a number of configuration options, not all of which are documented in the Build section of the docs. The VISIBILITY_HIDDEN option is on by default unless the ENABLE_PROXY option is on.

In build/, running:

cmake .. -DENABLE_ICD=OFF -DVISIBILITY_HIDDEN=OFF

and then:

make

the compile succeeds to the end. Then in build/lib/CL/ running:

nm libOpenCL.dylib | grep clBuildProgram

now prints:

0000000000013790 T _clBuildProgram