warning: macro expansion producing 'defined' has undefined behavior #2141
Description
In torch/csrc/generic/TensorMethods.cwrap we define a number of macros which are subsequently used in if statements:
#ifndef THC_GENERIC_FILE
#define IS_CUDA false
#define CUDA_FLOAT false
#else
#define IS_CUDA true
#define CUDA_BYTE defined(THC_REAL_IS_BYTE)
#define CUDA_CHAR defined(THC_REAL_IS_CHAR)
#define CUDA_SHORT defined(THC_REAL_IS_SHORT)
#define CUDA_INT defined(THC_REAL_IS_INT)
#define CUDA_LONG defined(THC_REAL_IS_LONG)
#define CUDA_FLOAT defined(THC_REAL_IS_FLOAT)
#define CUDA_DOUBLE defined(THC_REAL_IS_DOUBLE)
#define CUDA_HALF defined(THC_REAL_IS_HALF)
#endif
This is undefined. On clang 3.4.2, these warnings don't seem to actually get printed out (777 warnings generated.) but on clang 4.0.0 they seem to always get emitted.