Re-declaration of cmath functions in CUDA's math_functions.h - c++

Question

I included “cuda_runtime.h” in my project. It then raises compilation error:
In file included from /usr/local/cuda/include/common_functions.h:235:0,
from /usr/local/cuda/include/cuda_runtime.h:116,
from /usr/local/include/caffe2/core/common_gpu.h:7,
from /home/vpe.cripac/projects/LaS-VPE-Platform/src/native/DeepMAR_deploy/src/DeepMARCaffe2Utils.cpp:8:
/usr/local/cuda/include/math_functions.h:9421:99: error: redeclaration ‘float std::tanh(float)’ differs in ‘constexpr’
extern __DEVICE_FUNCTIONS_DECL__ __cudart_builtin__ __CUDA_CONSTEXPR__ float __cdecl tanh(float);
In file included from /usr/local/cuda/include/math_functions.h:8809:0,
from /usr/local/cuda/include/common_functions.h:235,
from /usr/local/cuda/include/cuda_runtime.h:116,
from /usr/local/include/caffe2/core/common_gpu.h:7,
from /home/vpe.cripac/projects/LaS-VPE-Platform/src/native/DeepMAR_deploy/src/DeepMARCaffe2Utils.cpp:8:
/usr/include/c++/4.8.2/cmath:520:3: error: from previous declaration ‘constexpr float std::tanh(float)’
tanh(float __x)
This happens both on Ubuntu and CentOS 7, using GCC 4.8.5 or 5.3.1.
Should I include any other header or define any macro before “cuda_runtime.h”?

Answer 1

You should never import math_functions.h into plain host code, and with g++ 4.8.5, I get an #error generated from within the header file if I try to do so. If you import cuda_runtime.h into your host code correctly, it will never import math_functions.h incorrectly:
$ cat test_math.cpp
#include <iostream>
#include <cmath>
#ifdef __BREAK_ME__
#include <math_functions.h>
#else
#include <cuda_runtime.h>
#endif
int main()
{
const float val = 0.123456789f;
std::cout << "tanh(" << val << ")=" << std::tanh(val) << std::endl;
return 0;
}
$ g++ -I/opt/cuda-8.0/include test_math.cpp
$ g++ -I/opt/cuda-8.0/include -D__BREAK_ME__ test_math.cpp
In file included from /opt/cuda-8.0/include/math_functions.h:10055:0,
from test_math.cpp:5:
/opt/cuda-8.0/include/crt/func_macro.h:50:2: error: #error -- incorrect inclusion of a cudart header file
#error -- incorrect inclusion of a cudart header file
^