Combining default_options : ['cpp_std=c++2a', 'cuda_std=c++17'] breaks nvcc

[drewrobson]

I'm trying to compile a project where the host code (.cpp) uses c++20, but the device code (.cu) uses c++17, since that is the latest version currently supported by nvcc.

Describe the bug
In meson.build, I tried this:

project('C++ std', 'cpp', 'cuda', version : '1.0.0', default_options : ['cpp_std=c++2a', 'cuda_std=c++17'])

but nvcc fails because it was called with --std=c++17 -std=c++2a:

meson compile -v
ninja: Entering directory `.'
[1/2] nvcc -Xcompiler=-Wall -Xcompiler=-Winvalid-pch -Xcompiler=-Wnon-virtual-dtor --std=c++17 -std=c++2a -g -G -g -I.. -I. -Iprog.p -Iprog.p -o prog.p/main.cu.o -c ../main.cu
FAILED: prog.p/main.cu.o 
nvcc -Xcompiler=-Wall -Xcompiler=-Winvalid-pch -Xcompiler=-Wnon-virtual-dtor --std=c++17 -std=c++2a -g -G -g -I.. -I. -Iprog.p -Iprog.p -o prog.p/main.cu.o -c ../main.cu
nvcc fatal   : Value 'c++2a' is not defined for option 'std'
ninja: build stopped: subcommand failed.

To Reproduce
Start with cuda example 6 std, but use this:
project('C++ std', 'cpp', 'cuda', version : '1.0.0', default_options : ['cpp_std=c++2a', 'cuda_std=c++17'])

Expected behavior
I expected that gcc would be invoked with c++2a and nvcc would be invoked with c++17.

If I manually remove the spurious -std=c++2a then nvcc succeeds.

system parameters
This is a native build on 5.4.101-1-MANJARO with Meson 0.57.1.

[obilaniu]

@drewrobson Can you have a try at my solution? It solves it on my end (except with c++17 and 14; I don't have c++2a)

[drewrobson]

Yep, that solves it on my end as well, with c++2a and c++17. Thank you for fixing this so quickly!