Fixes warning with GCC 10.2

[mfbalin]

The variable bufferRegion is already declared as const so there is no need for const inside reinterpret_cast.

[romanovvlad]

The variable bufferRegion is already declared as const so there is no need for const inside reinterpret_cast.

Could you please elaborate more on why it is a problem?
Tried to replicate the same situation on godbolt and see no warnings. https://godbolt.org/z/fKv6z5

[mfbalin]

I am getting the following error during compilation and it gets fixed when I remove the const there.

args:Namespace(base_branch=None, branch=None, build_number=None, build_parallelism='6', builder_dir=None, obj_dir=None, pr_number=None, src_dir=None)
[Cmake Command]: cmake --build /home/mfbalin/sycl_workspace/llvm/build -- deploy-sycl-toolchain deploy-opencl-aot -j 6
[10/1795] Performing update step for 'ocl-headers'
-- ocl-headers update command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-headers-prefix/src/ocl-headers-stamp/ocl-headers-update-*.log
[13/1795] Performing build step for 'ocl-headers'
-- ocl-headers build command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-headers-prefix/src/ocl-headers-stamp/ocl-headers-build-*.log
[16/1795] Performing update step for 'opencl-headers'
HEAD is up to date.
[17/1795] Performing update step for 'level-zero-loader'
-- level-zero-loader update command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/plugins/level_zero/level-zero-loader-prefix/src/level-zero-loader-stamp/level-zero-loader-update-*.log
[18/1795] Performing configure step for 'level-zero-loader'
-- level-zero-loader configure command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/plugins/level_zero/level-zero-loader-prefix/src/level-zero-loader-stamp/level-zero-loader-configure-*.log
[24/1795] Performing update step for 'ocl-icd'
-- ocl-icd update command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-icd-prefix/src/ocl-icd-stamp/ocl-icd-update-*.log
[27/1795] Performing configure step for 'ocl-icd'
-- ocl-icd configure command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-icd-prefix/src/ocl-icd-stamp/ocl-icd-configure-*.log
[28/1795] Performing update step for 'opencl-icd'
HEAD is up to date.
[29/1795] Performing configure step for 'opencl-icd'
-- Configuring done
-- Generating done
-- Build files have been written to: /home/mfbalin/sycl_workspace/llvm/build/tools/opencl-aot/icd_build
[30/1795] Performing build step for 'ocl-icd'
-- ocl-icd build command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-icd-prefix/src/ocl-icd-stamp/ocl-icd-build-*.log
[31/1795] Performing install step for 'ocl-icd'
-- ocl-icd install command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/ocl-icd-prefix/src/ocl-icd-stamp/ocl-icd-install-*.log
[34/1795] Performing build step for 'opencl-icd'
[1/4] Building C object CMakeFiles/OpenCL.dir/loader/linux/icd_linux.c.o
[2/4] Linking C shared library libOpenCL.so.1.2
[3/4] Creating library symlink libOpenCL.so.1 libOpenCL.so
[4/4] Linking C executable test/loader_test/icd_loader_test
[79/970] Performing build step for 'level-zero-loader'
-- level-zero-loader build command succeeded.  See also /home/mfbalin/sycl_workspace/llvm/build/tools/sycl/plugins/level_zero/level-zero-loader-prefix/src/level-zero-loader-stamp/level-zero-loader-build-*.log
[86/970] Building CXX object tools/sycl/plugins/cuda/CMakeFiles/pi_cuda.dir/pi_cuda.cpp.o
FAILED: tools/sycl/plugins/cuda/CMakeFiles/pi_cuda.dir/pi_cuda.cpp.o 
/usr/bin/c++  -DCL_TARGET_OPENCL_VERSION=220 -D_DEBUG -D_GLIBCXX_ASSERTIONS=1 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Dpi_cuda_EXPORTS -Itools/sycl/plugins/cuda -I/home/mfbalin/sycl_workspace/llvm/sycl/plugins/cuda -Iinclude -I/home/mfbalin/sycl_workspace/llvm/llvm/include -I/home/mfbalin/sycl_workspace/llvm/sycl/include -Itools/sycl/OpenCL/inc -isystem /usr/local/cuda/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -Wall -Wextra -Wno-deprecated-declarations -Werror -O3  -fPIC   -UNDEBUG -std=c++14 -MD -MT tools/sycl/plugins/cuda/CMakeFiles/pi_cuda.dir/pi_cuda.cpp.o -MF tools/sycl/plugins/cuda/CMakeFiles/pi_cuda.dir/pi_cuda.cpp.o.d -o tools/sycl/plugins/cuda/CMakeFiles/pi_cuda.dir/pi_cuda.cpp.o -c /home/mfbalin/sycl_workspace/llvm/sycl/plugins/cuda/pi_cuda.cpp
/home/mfbalin/sycl_workspace/llvm/sycl/plugins/cuda/pi_cuda.cpp: In function ‘pi_result cuda_piMemBufferPartition(pi_mem, pi_mem_flags, pi_buffer_create_type, void*, _pi_mem**)’:
/home/mfbalin/sycl_workspace/llvm/sycl/plugins/cuda/pi_cuda.cpp:1785:8: error: type qualifiers ignored on cast result type [-Werror=ignored-qualifiers]
 1785 |       *reinterpret_cast<const pi_buffer_region>(buffer_create_info);
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
[91/970] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.
Traceback (most recent call last):
  File "/home/mfbalin/sycl_workspace/llvm/buildbot/compile.py", line 67, in <module>
    ret = main()
  File "/home/mfbalin/sycl_workspace/llvm/buildbot/compile.py", line 63, in main
    return do_compile(args)
  File "/home/mfbalin/sycl_workspace/llvm/buildbot/compile.py", line 40, in do_compile
    subprocess.check_call(cmake_cmd, cwd=abs_obj_dir)
  File "/usr/lib/python3.8/subprocess.py", line 364, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['cmake', '--build', '/home/mfbalin/sycl_workspace/llvm/build', '--', 'deploy-sycl-toolchain', 'deploy-opencl-aot', '-j', '6']' returned non-zero exit status 1.```

[mfbalin]

I corrected my compiler version in the title

[mfbalin]

The variable bufferRegion is already declared as const so there is no need for const inside reinterpret_cast.

Could you please elaborate more on why it is a problem?
Tried to replicate the same situation on godbolt and see no warnings. https://godbolt.org/z/fKv6z5

see this https://godbolt.org/z/P3b5K5, actually this might fail to compile because of something else. I am not sure why such a warning I am getting is fixed by this simple change.

[mfbalin]

For more info, I am on a Ubuntu 20.04 system with g++ (Ubuntu 10.2.0-5ubuntu1~20.04) 10.2.0. Maybe only my compiler has this problem.

[mfbalin]

Actually, this reproduces the issue, I copied all compiler flags to compiler explorer to reproduce it.

https://godbolt.org/z/Yhq3P7

[mfbalin]

This has the least number of compiler flags that still fails to compile

https://godbolt.org/z/xs1Txv

[romanovvlad]

This has the least number of compiler flags that still fails to compile

https://godbolt.org/z/xs1Txv

Thank you, I also found some explanation here https://stackoverflow.com/questions/62733524/why-does-gcc-handle-a-const-reinterpret-cast-different-when-type-alias-is-used .