Different output when upgrading from clang 9 to clang 10

[adrianimboden]

What is the issue you have?

I just spent quite some time tracking down a bug caused by upgrading the compiler from clang 9.0.1 to clang 10.0. But I am not sure if that is a compiler bug or something else.
But I thought I should share it anyway here.

The following piece of code:

nlohmann::json config = {"config: {"value", {}}};
std::cerr << config.dump() << std::endl;

using clang 9.0.1 produces:

{"config": {"value": {}}}

and using clang 10.0.0 produces:

{"config": {"value": null}}

Which compiler and operating system are you using?

• Compiler: Clang 9.0.1/10.0.0, C++17, libc++
• Operating system: Ubuntu 20.04

Which version of the library did you use?

• [ x ] latest release version 3.7.3

[FrancoisChabot]

This also happens on the develop branch:
https://gcc.godbolt.org/z/937d5g

Honestly, I have no clue how clang 9.0.1 arrives at {} meaning "object", I just don't see a code path leading there at first glance. Also, considering both old and new gcc agree with clang 10.0.0, I'd be inclined to say that it's clang 9 that's wrong here.

see #2046

[nlohmann]

This is indeed a duplicate of #2046.

[adrianimboden]

Closing because of duplicate