Write doubles with the conversion of Zmij by Victor Zverovich (MIT),
ported to C++11 (detail/conversions/zmij.hpp). It finds the
shortest decimal that reads back as the same double, and the
closest one if there are several. Grisu2, used until now, is fast
but not always shortest: it sometimes writes a 17th digit where 16
suffice, or a last digit that is not the closest. The layout is
unchanged (1.5, 100.0, 1e+100, -0.0); float keeps Grisu2.
Digits are converted eight at a time with the BCD conversion of
Xiang JunBo, as in Zmij, and written with one byte swap per eight
digits and fixed-size moves instead of per-digit loops. Leading and
trailing zeros are counted from those bytes. to_chars() uses a
local buffer when the caller's is shorter than the 41 bytes this
may write. The powers of ten come from the number-parsing table,
adjusted where it holds values rounded up, and extended with Zmij's
compressed tables beyond 10^308.
write_shortest() converts its 16 digits in one vector register
(SSE2 on x86-64, NEON on 64-bit Arm, both baseline) and inserts the
decimal point inside the register, avoiding a store-forwarding
stall that cost about 25% of the time to write a double. dump()
writes floats and integers straight into the serializer's write
buffer instead of copying them from a member buffer, and small
integers eight digits at a time. read_eight_bytes() and
parse_eight_digits() are marked always-inline, which GCC had been
calling out of line in the number-parsing loops.
Of one million random doubles, about 0.14% are now written with
different digits, always to a value that still reads back as the
same double.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
MSVC warns with C5260 that kAlpha and kGamma have internal linkage when
the header is used as a header unit or through a module. JSON_INLINE_VARIABLE
makes them inline variables from C++17 on.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Route hand-rolled diagnostic pragmas through Hedley
Several places in the library hand-roll compiler diagnostic suppression
with raw `#pragma`/`#ifdef __GNUC__`/`#ifdef __clang__` guards instead of
using the Hedley primitives already bundled and used elsewhere
(JSON_HEDLEY_DIAGNOSTIC_PUSH/POP, JSON_HEDLEY_PRAGMA, ...). Converted six
of the seven listed push/pop pairs to use those primitives instead of
raw `#pragma GCC diagnostic`/`#pragma clang diagnostic` text:
- include/nlohmann/json.hpp (~3770, ~3863): -Wfloat-equal
- include/nlohmann/detail/conversions/to_chars.hpp (~1078): -Wfloat-equal
- include/nlohmann/detail/output/binary_writer.hpp (~1844): -Wfloat-equal
- include/nlohmann/detail/iterators/iteration_proxy.hpp (~211): -Wmismatched-tags
- include/nlohmann/detail/exceptions.hpp (~36): -Wweak-vtables
iteration_proxy.hpp did not previously include macro_scope.hpp itself
(it only compiled because some other header included earlier in
json.hpp happened to pull macro_scope.hpp in first); it now includes it
directly like the other detail headers that use Hedley macros, so it is
self-contained.
Each push/pop pair now uses JSON_HEDLEY_DIAGNOSTIC_PUSH/POP
unconditionally (a no-op on compilers that don't need it) and wraps the
actual `#pragma ... diagnostic ignored` text in JSON_HEDLEY_PRAGMA so it
goes through Hedley's _Pragma()-based emission instead of a raw #pragma
line, while keeping the original `#ifdef __GNUC__` / `#if
defined(__clang__)` guard around the ignored-pragma itself.
Deviation from the issue's suggested transformation: the issue's example
replaces the `#ifdef __GNUC__` guard with `#if
JSON_HEDLEY_HAS_WARNING("-Wfloat-equal")`. JSON_HEDLEY_HAS_WARNING is
implemented purely via Clang's `__has_warning` builtin and evaluates to
0 on real GCC (`#define JSON_HEDLEY_HAS_WARNING(warning) (0)` when
`__has_warning` is not defined), so adopting it verbatim would silently
stop suppressing -Wfloat-equal on GCC -- a real regression, not just a
style change. The existing `#ifdef __GNUC__` / `#if defined(__clang__)`
guards were kept for the ignored-pragma to stay behavior-preserving, and
only the push/pop/pragma-emission mechanism was routed through Hedley.
Two of the seven locations from the issue (the -Wignored-attributes
push at the very top of json.hpp and its matching pop after
`#include <nlohmann/detail/macro_unscope.hpp>`) were intentionally left
unconverted:
- The push, at the very top of json.hpp, runs before
`detail/macro_scope.hpp` (and therefore hedley.hpp) has been included
anywhere in the translation unit, so JSON_HEDLEY_DIAGNOSTIC_PUSH is not
yet defined at that point.
- The pop runs after `macro_unscope.hpp`, which -- via hedley_undef.hpp
-- has already #undef'd every JSON_HEDLEY_* macro (by design, see
#5408) precisely so they don't leak to users, so JSON_HEDLEY_DIAGNOSTIC_POP
is no longer defined by the time the pop is reached either.
Making this one pair work would require either hoisting the ~2000
line vendored hedley.hpp to the very top of the amalgamated single
header (a much bigger structural change to single_include than a pure
mechanism swap) or special-casing this one pop ahead of the general
macro cleanup. Both are riskier than the mechanical, behavior-preserving
change requested, so this pair was left as-is.
## Validation
- Compiled include/nlohmann/json.hpp and single_include/nlohmann/json.hpp
with `-Wall -Wextra -Wfloat-equal -Wmismatched-tags -Wweak-vtables`
(clang, which self-identifies as __GNUC__ too): no warnings, same as
before the change.
- Compiled and ran tests/src/unit-to_chars.cpp, unit-conversions.cpp,
unit-iterators1.cpp, unit-iterators2.cpp, and unit-class_parser.cpp
against the fixed include/: all pass.
- Compiled unit-msgpack.cpp, unit-bjdata.cpp, and unit-ubjson.cpp (which
exercise binary_writer.hpp's write_compact_float extensively): all
compile cleanly; the vast majority of assertions pass (the only
failures are pre-existing environment issues unrelated to this change
-- missing generated test-data files, not code correctness).
- Ran `make amalgamate`; the single_include diff is limited to exactly
the lines touched in include/, with no unrelated reordering.
- No real (non-Apple) GCC was available in this environment to test
directly; the `_Pragma("GCC diagnostic ...")` text emitted by
JSON_HEDLEY_PRAGMA is byte-identical to the prior `#pragma GCC
diagnostic ...` text, and the `#ifdef __GNUC__` guard is unchanged, so
GCC's behavior is expected to be identical. CI covers the GCC matrix.
This PR is stacked on top of #5475 (issue-5408-hedley-undef-leak) since
both touch the same files; only the last commit here is new.
Fixes#5409.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Guard JSON_HEDLEY_DIAGNOSTIC_PUSH/POP with the same compiler check as the pragma they bracket
Addresses review feedback from @gregmarr on PR #5485: the push/pop calls
were unconditional, so compilers other than the one the ignored-pragma
targets (e.g. MSVC, or GCC where the pair only applies under __clang__)
now did a needless push/pop with nothing suppressed in between. Move the
existing #ifdef __GNUC__ / #if defined(__clang__) guard to also cover the
push/pop, restoring the original zero-overhead behavior on other compilers
while still emitting the pragma itself through Hedley.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Add versioned inline namespace
Add a versioned inline namespace to prevent ABI issues when linking code
using multiple library versions.
* Add namespace macros
* Encode ABI information in inline namespace
Add _diag suffix to inline namespace if JSON_DIAGNOSTICS is enabled, and
_ldvcmp suffix if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON is enabled.
* Move ABI-affecting macros into abi_macros.hpp
* Move std_fs namespace definition into std_fs.hpp
* Remove std_fs namespace from unit test
* Format more files in tests directory
* Add unit tests
* Update documentation
* Fix GDB pretty printer
* fixup! Add namespace macros
* Derive ABI prefix from NLOHMANN_JSON_VERSION_*
* Rename 'develop' folder to 'include/nlohmann'
* Rename 'src' folder to 'single_include/nlohmann'
* Use <nlohmann/*> headers in sources and tests
* Change amalgamate config file
Niels Lohmann
Florian Albrechtskirchinger
Niels Lohmann
Sven Fink
chenguoping
Florian Pigorsch
Ferenc Nasztanovics
Julius Rakow
Théo DELRIEU