compile error with clang

[CoinCheung]

Note: Providing complete information in the most concise form is the best way to get help. This issue template serves as the checklist for essential information to most of the technical issues and bug reports. For non-technical issues and feature requests, feel free to present the information in what you believe is the best form.

For Q & A and discussion, please start a discussion thread at https://discuss.mxnet.io

Description

I can compile successfully with g++ but error appears with clang.

Environment info (Required)

----------Python Info----------
Version      : 3.6.3
Compiler     : GCC 7.2.0
Build        : ('default', 'Oct 24 2017 14:48:20')
Arch         : ('64bit', '')
------------Pip Info-----------
Version      : 9.0.1
Directory    : /usr/lib/python3.6/site-packages/pip
----------MXNet Info-----------
No MXNet installed.
----------System Info----------
Platform     : Linux-4.13.12-1-ARCH-x86_64-with-arch
system       : Linux
node         : Arch-R720
release      : 4.13.12-1-ARCH
version      : #1 SMP PREEMPT Wed Nov 8 11:54:06 CET 2017
----------Hardware Info----------
machine      : x86_64
processor    : 
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  1
Core(s) per socket:  4
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               158
Model name:          Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz
Stepping:            9
CPU MHz:             3283.002
CPU max MHz:         3500.0000
CPU min MHz:         800.0000
BogoMIPS:            4993.00
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
NUMA node0 CPU(s):   0-3
Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp
----------Network Test----------
Setting timeout: 10
Timing for MXNet: https://github.com/apache/incubator-mxnet, DNS: 0.0252 sec, LOAD: 1.2449 sec.
Timing for Gluon Tutorial(en): http://gluon.mxnet.io, DNS: 0.1978 sec, LOAD: 6.1024 sec.
Timing for Gluon Tutorial(cn): https://zh.gluon.ai, DNS: 1.0039 sec, LOAD: 9.4451 sec.
Timing for FashionMNIST: https://apache-mxnet.s3-accelerate.dualstack.amazonaws.com/gluon/dataset/fashion-mnist/train-labels-idx1-ubyte.gz, DNS: 0.1305 sec, LOAD: 1.4144 sec.
Timing for PYPI: https://pypi.python.org/pypi/pip, DNS: 0.0125 sec, LOAD: 7.6978 sec.
Timing for Conda: https://repo.continuum.io/pkgs/free/, DNS: 0.0104 sec, LOAD: 0.6309 sec.

Package used (Python/R/Scala/Julia):
(I'm using c++)

For Scala user, please provide:

1. Java version: (java -version)
2. Maven version: (mvn -version)
3. Scala runtime if applicable: (scala -version)

For R user, please provide R sessionInfo():

Build info (Required if built from source)

Compiler (gcc/clang/mingw/visual studio):
clang
MXNet commit hash:
17427d1

Build config:

export CC = gcc
export CXX = clang++
export NVCC = nvcc

# whether compile with options for MXNet developer
DEV = 0

# whether compile with debug
DEBUG = 0

# whether compile with profiler
USE_PROFILER =

# whether to turn on segfault signal handler to log the stack trace
USE_SIGNAL_HANDLER =

# the additional link flags you want to add
ADD_LDFLAGS =

# the additional compile flags you want to add
ADD_CFLAGS =

#---------------------------------------------
# matrix computation libraries for CPU/GPU
#---------------------------------------------

# whether use CUDA during compile
USE_CUDA = 1

# add the path to CUDA library to link and compile flag
# if you have already add them to environment variable, leave it as NONE
# USE_CUDA_PATH = /usr/local/cuda
USE_CUDA_PATH = /opt/cuda

# whether use CuDNN R3 library
USE_CUDNN = 1

#whether to use NCCL library
USE_NCCL = 0
#add the path to NCCL library
USE_NCCL_PATH = NONE

# whether use opencv during compilation
# you can disable it, however, you will not able to use
# imbin iterator
USE_OPENCV = 1

#whether use libjpeg-turbo for image decode without OpenCV wrapper
USE_LIBJPEG_TURBO = 0
#add the path to libjpeg-turbo library
USE_LIBJPEG_TURBO_PATH = NONE

# use openmp for parallelization
USE_OPENMP = 1

# MKL ML Library for Intel CPU/Xeon Phi
# Please refer to MKL_README.md for details

# MKL ML Library folder, need to be root for /usr/local
# Change to User Home directory for standard user
# For USE_BLAS!=mkl only
MKLML_ROOT=/usr/local

# whether use MKL2017 library
USE_MKL2017 = 0

# whether use MKL2017 experimental feature for high performance
# Prerequisite USE_MKL2017=1
USE_MKL2017_EXPERIMENTAL = 0

# whether use NNPACK library
USE_NNPACK = 0

# choose the version of blas you want to use
# can be: mkl, blas, atlas, openblas
# in default use atlas for linux while apple for osx
UNAME_S := $(shell uname -s)
ifeq ($(UNAME_S), Darwin)
USE_BLAS = apple
else
USE_BLAS = openblas
endif

# whether use lapack during compilation
# only effective when compiled with blas versions openblas/apple/atlas/mkl
USE_LAPACK = 1

# path to lapack library in case of a non-standard installation
USE_LAPACK_PATH = 

# by default, disable lapack when using MKL
# switch on when there is a full installation of MKL available (not just MKL2017/MKL_ML)
ifeq ($(USE_BLAS), mkl)
USE_LAPACK = 1
endif

# add path to intel library, you may need it for MKL, if you did not add the path
# to environment variable
USE_INTEL_PATH = NONE

# If use MKL only for BLAS, choose static link automatically to allow python wrapper
ifeq ($(USE_MKL2017), 0)
ifeq ($(USE_BLAS), mkl)
USE_STATIC_MKL = 1
endif
else
USE_STATIC_MKL = NONE
endif

#----------------------------
# Settings for power and arm arch
#----------------------------
ARCH := $(shell uname -a)
ifneq (,$(filter $(ARCH), armv6l armv7l powerpc64le ppc64le aarch64))
	USE_SSE=0
else
	USE_SSE=1
endif

#----------------------------
# distributed computing
#----------------------------

# whether or not to enable multi-machine supporting
USE_DIST_KVSTORE = 0

# whether or not allow to read and write HDFS directly. If yes, then hadoop is
# required
USE_HDFS = 0

# path to libjvm.so. required if USE_HDFS=1
LIBJVM=$(JAVA_HOME)/jre/lib/amd64/server

# whether or not allow to read and write AWS S3 directly. If yes, then
# libcurl4-openssl-dev is required, it can be installed on Ubuntu by
# sudo apt-get install -y libcurl4-openssl-dev
USE_S3 = 0

#----------------------------
# performance settings
#----------------------------
# Use operator tuning
USE_OPERATOR_TUNING = 1

# Use gperftools if found
USE_GPERFTOOLS = 1

# Use JEMalloc if found, and not using gperftools
USE_JEMALLOC = 1

#----------------------------
# additional operators
#----------------------------

# path to folders containing projects specific operators that you don't want to put in src/operators
EXTRA_OPERATORS =

#----------------------------
# other features
#----------------------------

# Create C++ interface package
USE_CPP_PACKAGE = 1

#----------------------------
# plugins
#----------------------------

# whether to use caffe integration. This requires installing caffe.
# You also need to add CAFFE_PATH/build/lib to your LD_LIBRARY_PATH
# CAFFE_PATH = $(HOME)/caffe
# MXNET_PLUGINS += plugin/caffe/caffe.mk

# WARPCTC_PATH = $(HOME)/warp-ctc
# MXNET_PLUGINS += plugin/warpctc/warpctc.mk

# whether to use sframe integration. This requires build sframe
# git@github.com:dato-code/SFrame.git
# SFRAME_PATH = $(HOME)/SFrame
# MXNET_PLUGINS += plugin/sframe/plugin.mk

Error Message:

clang++ -std=c++11 -c -DMSHADOW_FORCE_STREAM -Wall -Wsign-compare -O3 -DNDEBUG=1 -I/home/coin/build/mxnet/mshadow/ -I/home/coin/build/mxnet/dmlc-core/include -fPIC -I/home/coin/build/mxnet/nnvm/include -I/home/coin/build/mxnet/dlpack/include -Iinclude -funroll-loops -Wno-unused-variable -Wno-unused-parameter -Wno-unknown-pragmas -Wno-unused-local-typedefs -msse3 -I/opt/cuda/include -DMSHADOW_USE_CBLAS=1 -DMSHADOW_USE_MKL=0 -DMSHADOW_RABIT_PS=0 -DMSHADOW_DIST_PS=0 -DMSHADOW_USE_PASCAL=0 -DMXNET_USE_OPENCV=1 -I/usr/include/opencv -fopenmp -DMXNET_USE_OPERATOR_TUNING=1 -DMXNET_USE_LAPACK=1 -DMSHADOW_USE_CUDNN=1 -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-free  -I/home/coin/build/mxnet/3rdparty/cub -DMXNET_USE_NCCL=0 -DMXNET_USE_LIBJPEG_TURBO=0 -MMD -c src/operator/random/multisample_op.cc -o build/src/operator/random/multisample_op.o
In file included from src/operator/random/multisample_op.cc:26:
In file included from src/operator/random/./multisample_op.h:34:
src/operator/random/./sampler.h:93:10: error: use of undeclared identifier
      'omp_get_num_threads'
  return omp_get_num_threads();
         ^
1 error generated.
make: *** [Makefile:372: build/src/operator/random/multisample_op.o] Error 1

Minimum reproducible example

I just compile the library by running

make

Steps to reproduce

(Paste the commands you ran that produced the error.)

1. clean all

make clean

2. recompile

make

What have you tried to solve it?

[mwbyeon]

@CoinCheung
clang++ compiler does not support OpenMP. you have to disable it. set USE_OPENMP=0.
if you want to run with clang and openmp, try with clang-omp(https://clang-omp.github.io/).

[jakirkham]

Clang 3.7+ has OpenMP support. Though it is a separate library and not all installs ship it (e.g. Apple's copy for instance). However it is trivial to build yourself. Also you can get copies of the complete Clang toolchain from your package manager of choice or Anaconda if you use that.

[hubutui]

Any updates? I also try to compile mxnet with clang to avoid ABI issue. But even I specifiy CC=clang CXX=clang++, the compiling will use gcc somewhere, and I got unrecognize -fopenmp=libopenmp error:

[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/infer_shape_type.cc.o
[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/order_mutation.cc.o
[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/place_device.cc.o
[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/plan_memory.cc.o
[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/print_graph_ir.cc.o
[ 70%] Building CXX object CMakeFiles/mxnet_static.dir/3rdparty/tvm/nnvm/src/pass/saveload_json.cc.o
[ 70%] Building CUDA object CMakeFiles/mxnet_static.dir/src/common/random_generator.cu.o
gcc: error: unrecognized command line option ‘-fopenmp=libomp’; did you mean ‘-fopenmp-simd’?
make[2]: *** [CMakeFiles/mxnet_static.dir/build.make:3872: CMakeFiles/mxnet_static.dir/src/common/random_generator.cu.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:88: CMakeFiles/mxnet_static.dir/all] Error 2
make: *** [Makefile:130: all] Error 2