Niels Lohmann c8e0f8a249 Gate the C++20 iterator classification on JSON_HAS_RANGES ...

Making supports_bulk_scan depend on iterator_is_contiguous meant the trait
is now instantiated for every adapter, not only when get_elements() is
called. On standard libraries with an incomplete <ranges> that is fatal:
libstdc++ 10 evaluates std::contiguous_iterator<std::counted_iterator<T*>>
by calling std::to_address, which needs an operator-> its counted_iterator
does not have, so satisfaction checking is a hard error rather than false.
Reported by clang 14 + libstdc++ 10.

JSON_HAS_RANGES already encodes exactly this ("libstdc++ < 11 has incomplete
C++20 ranges", #4440), so require it for the C++20 branch. Affected
toolchains fall back to the pointer-only test and the byte-at-a-time
scanner, which parses identically, just without the bulk fast paths.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

2026-08-20 03:46:03 +02:00

..

nlohmann

Gate the C++20 iterator classification on JSON_HAS_RANGES

2026-08-20 03:46:03 +02:00