Make PYBIND11_CPP_STANDARD work under MSVC

Under MSVC we were ignoring PYBIND11_CPP_STANDARD and simply not
passing any standard (which makes MSVC default to its C++14 mode).

MSVC 2015u3 added the `/std:c++14` and `/std:c++latest` flags; the
latter, under MSVC 2017, enables some C++17 features (such as
`std::optional` and `std::variant`), so it is something we need to
start supporting under MSVC.

This makes the PYBIND11_CPP_STANDARD cmake variable work under MSVC,
defaulting it to /std:c++14 (matching the default -std=c++14 for
non-MSVC).

It also adds a new appveyor test running under MSVC 2017 with
/std:c++latest, which runs (and passes) the
`std::optional`/`std::variant` tests.

Also updated the documentation to clarify the c++ flags and add show
MSVC flag examples.
This commit is contained in:
Jason Rhinelander 2017-05-09 14:37:48 -04:00
parent ca0e82b79f
commit 77710ff01c
3 changed files with 41 additions and 19 deletions

View File

@ -11,11 +11,20 @@ platform:
environment:
matrix:
- CONDA: 36
CPP: 14
- CONDA: 27
CPP: 14
- CONDA: 36
CPP: latest
matrix:
exclude:
- image: Visual Studio 2015
platform: x86
- image: Visual Studio 2015
CPP: latest
- image: Visual Studio 2017
CPP: latest
platform: x86
install:
- ps: |
if ($env:PLATFORM -eq "x64") { $env:CMAKE_ARCH = "x64" }
@ -37,7 +46,7 @@ install:
7z x 3.3.3.zip -y > $null
$env:CMAKE_INCLUDE_PATH = "eigen-eigen-67e894c6cd8f"
build_script:
- cmake -G "%CMAKE_GENERATOR%" -A "%CMAKE_ARCH%" -DPYBIND11_WERROR=ON -DCMAKE_SUPPRESS_REGENERATION=1
- cmake -G "%CMAKE_GENERATOR%" -A "%CMAKE_ARCH%" -DPYBIND11_CPP_STANDARD=/std:c++%CPP% -DPYBIND11_WERROR=ON -DCMAKE_SUPPRESS_REGENERATION=1
- set MSBuildLogger="C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
- cmake --build . --config Release --target pytest -- /v:m /logger:%MSBuildLogger%
- cmake --build . --config Release --target test_cmake_build -- /v:m /logger:%MSBuildLogger%

View File

@ -92,17 +92,28 @@ regular LTO if ``-flto=thin`` is not available.
Configuration variables
-----------------------
By default, pybind11 will compile modules with the latest C++ standard
available on the target compiler. To override this, the standard flag can
be given explicitly in ``PYBIND11_CPP_STANDARD``:
By default, pybind11 will compile modules with the C++14 standard, if available
on the target compiler, falling back to C++11 if C++14 support is not
available. Note, however, that this default is subject to change: future
pybind11 releases are expected to migrate to newer C++ standards as they become
available. To override this, the standard flag can be given explicitly in
``PYBIND11_CPP_STANDARD``:
.. code-block:: cmake
# Use just one of these:
# GCC/clang:
set(PYBIND11_CPP_STANDARD -std=c++11)
set(PYBIND11_CPP_STANDARD -std=c++14)
set(PYBIND11_CPP_STANDARD -std=c++1z) # Experimental C++17 support
# MSVC:
set(PYBIND11_CPP_STANDARD /std:c++14)
set(PYBIND11_CPP_STANDARD /std:c++latest) # Enables some MSVC C++17 features
add_subdirectory(pybind11) # or find_package(pybind11)
Note that this and all other configuration variables must be set **before** the
call to ``add_subdiretory`` or ``find_package``. The variables can also be set
call to ``add_subdirectory`` or ``find_package``. The variables can also be set
when calling CMake from the command line using the ``-D<variable>=<value>`` flag.
The target Python version can be selected by setting ``PYBIND11_PYTHON_VERSION``

View File

@ -19,7 +19,8 @@ include(CheckCXXCompilerFlag)
include(CMakeParseArguments)
function(select_cxx_standard)
if(NOT MSVC AND NOT PYBIND11_CPP_STANDARD)
if(NOT PYBIND11_CPP_STANDARD)
if(NOT MSVC)
check_cxx_compiler_flag("-std=c++14" HAS_CPP14_FLAG)
check_cxx_compiler_flag("-std=c++11" HAS_CPP11_FLAG)
@ -30,9 +31,12 @@ function(select_cxx_standard)
else()
message(FATAL_ERROR "Unsupported compiler -- pybind11 requires C++11 support!")
endif()
elseif(MSVC)
set(PYBIND11_CPP_STANDARD /std:c++14)
endif()
set(PYBIND11_CPP_STANDARD ${PYBIND11_CPP_STANDARD} CACHE STRING
"C++ standard flag, e.g. -std=c++11 or -std=c++14. Defaults to latest available." FORCE)
"C++ standard flag, e.g. -std=c++11, -std=c++14, /std:c++14. Defaults to C++14 mode." FORCE)
endif()
endfunction()
@ -162,10 +166,8 @@ function(pybind11_add_module target_name)
endif()
select_cxx_standard()
if(NOT MSVC)
# Make sure C++11/14 are enabled
target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD})
endif()
if(ARG_NO_EXTRAS)
return()