Niels Lohmann 4b027c9ea3 Fix to_msgpack() reading the inactive number union member ...

basic_json stores number_integer and number_unsigned in a union, and
number_unsigned_t only has to be at least as wide as number_integer_t
(with the default types, both are 64-bit and have the same
representation). When number_integer_t is narrower, write_msgpack()
read the wrong union member in two places:

- The number_unsigned case wrote number_integer's bits instead of
  number_unsigned's, silently writing the wrong value whenever it
  did not fit in number_integer_t.
- The number_integer case (non-negative branch) picked the encoded
  width by comparing number_unsigned's bits, which is undefined
  behavior, though the value written was still number_integer's, so
  at worst a too-wide encoding was chosen.

Read the active member in both cases, like the other binary writers
(CBOR, UBJSON, BJData, BSON, BON8) already do.

Fixes #5644.

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

2026-09-29 23:38:43 +02:00

..

json_fwd.hpp

Make JSON_STRICT_NUL_HANDLING part of the ABI tag (#5560)

2026-09-25 21:54:11 +02:00

json.hpp

Fix to_msgpack() reading the inactive number union member

2026-09-29 23:38:43 +02:00