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Niels Lohmann
42f89e3130
* Let to_json(std::optional<T>) propagate exceptions from T's to_json The overload was marked noexcept even though its body assigns *opt to the JSON value, which calls T's to_json (or allocates for std::string, std::vector, or json). Any exception from there -- a user-defined to_json reporting an error, or std::bad_alloc -- called std::terminate() instead of propagating. The noexcept also made basic_json's converting constructor noexcept(true) for std::optional<T>, so json j = opt; could not report the error either. Fixes #5642. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Fix CI: make to_json(std::optional<T>) conditionally noexcept GCC's -Wnoexcept (an error in ci_test_gcc) fired at to_json_fn's noexcept(noexcept(to_json(j, val))): after dropping the unconditional noexcept, to_json(std::optional<int>) had no exception specification although GCC could prove its body cannot throw. It also made json(std::optional<int>) lose its noexcept. Declare the overload noexcept exactly when assigning the contained value to the JSON value is (std::is_nothrow_assignable<BasicJsonType&, const T&>), which is what the body does. std::optional<int> is noexcept again; a T whose to_json may throw still propagates the exception. Static assertions in the test check both cases. The test's throwing to_json triggered -Wmissing-prototypes and -Wmissing-noreturn (clang) and -Wmissing-declarations and -Wsuggest-attribute=noreturn (GCC). Move the type and its to_json into an anonymous namespace, mark the function [[noreturn]], and compile them only without JSON_NOEXCEPTION, like the test that uses them. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>