Making them trivially copyable allows using std::memcpy() without undefined
behaviors.
Only Matrix and Array with trivially copyable DenseStorage are marked as
trivially copyable with an additional type trait.
As described in http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0848r3.html
it requires extremely verbose SFINAE to make the special member functions of
fixed-size Matrix and Array trivial, unless C++20 concepts are available to
simplify the selection of trivial special member functions given template
parameters. Therefore only make this feature available to compilers that support
C++20 P0848R3.
Fix#1855.
The following preprocessor macros are added:
- EIGEN_COMP_CPE and EIGEN_COMP_CLANGCPE version number of the CRAY compiler if
Eigen is compiled with the Cray C++ compiler, 0 otherwise.
- EIGEN_COMP_FCC and EIGEN_COMP_CLANGFCC version number of the FCC compiler if
Eigen is compiled with the Fujitsu C++ compiler, 0 otherwise
- EIGEN_COMP_CLANGICC version number of the ICX compiler if Eigen is compiled
with the Intel oneAPI C++ compiler, 0 otherwise
All three compilers (Cray, Fujitsu, Intel) offer a traditional and a Clang-based
frontend. This is distinguished by the CLANG prefix.
Looks like we need to update the
`EIGEN_INHERIT_ASSIGNMENT_EQUAL_OPERATOR` for newer versions of MSVC as
well when compiling with NVCC. Fixes build issues for VS 2017.
CUDA 9 seems to require labelling defaulted constructors as
`EIGEN_DEVICE_FUNC`, despite giving warnings that such labels are
ignored. Without these labels, the `gpu_basic` test fails to
compile, with errors about calling `__host__` functions from
`__host__ __device__` functions.
GCC 4.8 doesn't seem to like the `g` register constraint, failing to
compile with "error: 'asm' operand requires impossible reload".
Tested `r` instead, and that seems to work, even with latest compilers.
Also fixed some minor macro issues to eliminate warnings on armv7.
Fixes#2315.
Details are scattered across #920, #1000, #1324, #2291.
Summary: some MSVC versions have a bug that requires omitting explicit
`operator=` definitions (leads to duplicate definition errors), and
some MSVC versions require adding explicit `operator=` definitions
(otherwise implicitly deleted errors). This mess tries to cover
all the cases encountered.
Fixes#2291.
