* Broaden JSON_HEDLEY_WARN_UNUSED_RESULT coverage to pure query functions
Add JSON_HEDLEY_WARN_UNUSED_RESULT to the unambiguous, const,
side-effect-free observer functions whose return value is the entire
purpose of the call:
- dump()
- type(), type_name()
- all is_* predicates (is_primitive, is_structured, is_null,
is_boolean, is_number, is_number_integer, is_number_unsigned,
is_number_float, is_object, is_array, is_string, is_binary,
is_discarded)
- empty(), size(), max_size()
- count(...) (both overloads) and contains(...) (all overloads,
including the deprecated json_pointer<BasicJsonType> overload)
This mirrors the direction the standard library has taken with
[[nodiscard]] on the analogous std::vector/std::map members, and
catches real bugs such as `j.empty();` (meant `j.clear();`) or
`j.contains(k);` with the result thrown away.
Deliberately out of scope (left for a separate, later policy
decision, per the issue): at(), value(), get*(), flatten(),
unflatten(), patch(), merge_patch(), begin()/end(), comparison
operators, erase(), and emplace().
Compiling the full test suite (tests/src/unit-*.cpp) with
-Wunused-result -Werror uncovered one real hit: a regression test in
unit-regression2.cpp called dump() purely to check it does not throw,
discarding the result. Fixed by explicitly casting to void, since the
call is intentionally result-less there.
Fixes#5410
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix discarded nodiscard results across the test suite for GCC's warn_unused_result
A plain (void) cast on a call expression suppresses the C++17 [[nodiscard]]
warning but not GCC's warning for functions annotated via the GNU
__attribute__((warn_unused_result)) form -- which is what
JSON_HEDLEY_WARN_UNUSED_RESULT expands to on GCC. Several existing tests
that call a newly-annotated function (dump(), empty()) purely to check
that it throws/does not throw, discarding the result via (void), newly
warned (and failed -Werror builds) once the annotation was broadened.
Route those discards through a small ignore_return_value() helper
instead, which actually consumes the value and suppresses the warning
on both attribute forms.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Use utils::ignore_return_value() for the issue #1445 dump() discard too
Addresses review feedback from @gregmarr on PR #5477: this call site was
still using the older "capture in a variable, then (void) it" pattern
from before this PR introduced utils::ignore_return_value(), instead of
the helper now used at every other discarded-nodiscard-result call site
this PR touches.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Move UDLs into nlohmann::literals::json_literals namespace
* Add 'using namespace' to unit tests
* Add 'using namespace' to examples
* Add 'using namespace' to README
* Move UDL mkdocs pages out of basic_json/
* Update documentation
* Update docset index
* Add JSON_GlobalUDLs CMake option
* Add unit test
* Build examples without global UDLs
* Add CI target
Use DOCTEST_* macros in place of predefined compiler macros for compiler
detection and version checks.
The suppression of warning -Wrange-loop-construct in unit-items.cpp
causes GCC<11 to warn about pragmas. Suppressed by adding a version
check.
Niels Lohmann
Harinath Nampally
Colby Haskell
Florian Albrechtskirchinger