Incompatible with USD 23.11 and C++17

[dgovil]

Describe the issue
When trying to build Maya USD against USD 23.11, I'm hitting two issues.

1. USD 23.11 uses C++17, and Maya USD doesn't specify a CXX standard , so fails to support new C++17 features
2. The Boost version that aligns with Maya 2024 doesn't support new clang versions because it assumes deprecated functions are still available. See Building with C++17 standard and Boost results in use of removed functions PixarAnimationStudios/OpenUSD#2634

The change to make both work would be simply adding the following:

set(CMAKE_CXX_STANDARD 17)
add_compile_definitions(BOOST_NO_CXX98_FUNCTION_BASE)

While a PR would be small and minimal, I didn't want to make these assumptions as something Autodesk wants across the board.

• Maya USD commit SHA 1248684

[seando-adsk]

Actually we do set the CXX standard here: https://github.com/Autodesk/maya-usd/blob/dev/cmake/compiler_config.cmake#L90
I am working on updating our internal builds to USD 23.11. For that I have changed this line to:

            # USD updated to c++17 for USD v23.11
            $<IF:$<VERSION_GREATER_EQUAL:${USD_VERSION},0.23.11>,cxx_std_17,cxx_std_14>

I'm not sure about the var BOOST_NO_CXX98_FUNCTION_BASE. We won't be updating USD for Maya 2024 (it will remain at 22.11). Will adding that var have an impact on our preflight builds with previous Maya's that use older USD builds?

Sean

[dgovil]

Ah I'd done a grep for CMAKE_CXX_STANDARD and missed that.
Regarding BOOST_NO_CXX98_FUNCTION_BASE, I don't think it should have a negative effect on older Maya builds.

Sunya had done this in USD with this note

# Parts of boost (in particular, boost::hash) rely on deprecated features
# of the STL that have been removed from some implementations under C++17.
# This define tells boost not to use those features.
#
# Under Visual Studio, boost automatically detects that this flag is
# needed so we don't need to define it ourselves. Otherwise, we'll get a
# C4005 macro redefinition warning.
if (NOT MSVC)
    _add_define(BOOST_NO_CXX98_FUNCTION_BASE)
endif()

So it seems like what might make sense is that if both these conditions are true, then the variable is set:

• Using anything except MSVC
• Using C++17 or higher

That would leave your older builds alone

[seando-adsk]

Do we need that flag for only clang, or gcc as well? I can incorporate this into my changes.

Sean

[dgovil]

GCC would need it as well