/std:c++11 is not a valid MSVC compiler flag

[Simran-B]

Bug Report

Build Problem

The root CMakeLists.txt tries to set C++11 as standard for pybind11:

if(MSVC)
    set(PYBIND11_CPP_STANDARD /std:c++11)

However, MSVC does not support this argument:

cl : Command line warning D9002: ignoring unknown option "/std:c++11"

https://docs.microsoft.com/en-us/cpp/build/reference/std-specify-language-standard-version?view=msvc-160

C++ 11 support in Visual Studio should be turned on by default. [source]

[...] msvc (and clang) [are] missing a dedicated c++11 std compiler switch (msvc automagically detects if code is using C++11 or C++03 etc.) [source]

Beware: /std:c11 sets C11 as standard, not C++11!

To Reproduce

1. Operating System: Windows 10
2. Python version: 2.7.18
3. Example snippet that demonstrates the issue - if it's a build issue:

   cmake .. -G "Visual Studio 16 2019"
   cmake --build . --config Release
   

4. OpenTimelineIO release version or commit hash: 22945fd
5. Compiler information:
   Microsoft (R) C/C++-Optimierungscompiler Version 19.28.29333 für x64

Expected Behavior

There seem to be two options:

1. Not set this option at all for MSVC
2. Use target_compile_features(pybind11 PRIVATE cxx_std_11) (source) to let CMake handle it automatically

Logs

Microsoft (R)-Build-Engine, Version 16.8.1+bd2ea1e3c für .NET Framework
Copyright (C) Microsoft Corporation. Alle Rechte vorbehalten.

  Checking Build System
  Auto build dll exports
  opentime.vcxproj -> C:\Daten\Olive\Deps\OpenTimelineIO\build6\src\opentime\Release\opentime.dll
  Auto build dll exports
  opentimelineio.vcxproj -> C:\Daten\Olive\Deps\OpenTimelineIO\build6\src\opentimelineio\Release\opentimelineio.dll
cl : befehlszeile warning D9002: Unbekannte Option "/std:c++11" wird ignoriert. [C:\Daten\Olive\Deps\OpenTimelineIO\bui
ld6\src\py-opentimelineio\opentime-bindings\_opentime.vcxproj]
cl : befehlszeile warning D9002: Unbekannte Option "/std:c++11" wird ignoriert. [C:\Daten\Olive\Deps\OpenTimelineIO\bui
ld6\src\py-opentimelineio\opentime-bindings\_opentime.vcxproj]
  opentime_bindings.cpp
cl : befehlszeile warning D9002: Unbekannte Option "/std:c++11" wird ignoriert. [C:\Daten\Olive\Deps\OpenTimelineIO\bui
ld6\src\py-opentimelineio\opentime-bindings\_opentime.vcxproj]
  opentime_rationalTime.cpp
cl : befehlszeile warning D9002: Unbekannte Option "/std:c++11" wird ignoriert. [C:\Daten\Olive\Deps\OpenTimelineIO\bui
ld6\src\py-opentimelineio\opentime-bindings\_opentime.vcxproj]
  opentime_timeRange.cpp
cl : befehlszeile warning D9002: Unbekannte Option "/std:c++11" wird ignoriert. [C:\Daten\Olive\Deps\OpenTimelineIO\bui
ld6\src\py-opentimelineio\opentime-bindings\_opentime.vcxproj]
  opentime_timeTransform.cpp

[meshula]

Confirmed the issue, it's a warning not an error, which is why it's not being flagged by the CI. It seems like everything builds fine, so perhaps the best answer is to simply delete the line.

[meshula]

Fixed! Thanks for the report