chars_format::javascript follows the strict-mode grammar, which rejects
any leading zero. In sloppy mode, JavaScript also accepts a leading zero
when one of the digits is 8 or 9 ("08.5" is 8.5, Annex B's
NonOctalDecimalIntegerLiteral). A leading zero followed only by octal
digits is a LegacyOctalIntegerLiteral ("0775"), which is not a decimal
number: it is rejected with the new parse_error::legacy_octal_integer_part
so the caller can parse it in base 8.
javascript_sloppy sets one extra bit on top of javascript, and the check
lives inside the existing runtime JavaScript branch of
parse_number_string<false>, so the general path is unchanged. An
interleaved A/B with realbenchmark on canada.txt and mesh.txt (ASCII and
UTF-16, 32/64-bit) shows identical instructions per float and cycles
within noise.
Document both formats in the README.
The JSON format rejects leading zeros, which JavaScript also rejects,
but it further requires digits on both sides of the decimal point,
which JavaScript does not: ".5", "5." and "5.e3" are all valid
DecimalLiteral productions. Users lexing JavaScript therefore could not
use chars_format::json and had to re-check the integer span themselves
after a general-mode parse.
chars_format::javascript is general mode plus the leading-zero rule
(reported as leading_zeros_in_integer_part), with no_infnan. It is a
runtime check on the format, like fortran, so it reuses the existing
parse_number_string<false> instantiation. A leading minus sign is
accepted, and a leading plus sign with allow_leading_plus.
Claude-Session: https://claude.ai/code/session_01KbAWRBpE3MPy5cXECc5vWZ
Replace C-style casts with static_cast/const_cast so -Wold-style-cast
is clean, and enable that warning in the Unix test builds and the
amalgamated-header CI job.
The previous commit detects multi-wrap u64 overflow at the max_digits
boundary by re-parsing the digits through a checked multiply-add loop
(O(max_digits)). Replace that with the constant-time check used in
simdjson: the leading digit plus a single threshold comparison.
For a max_digits-length value, min_safe_u64(base) == base^(max_digits-1)
is the smallest such value and also the width of each leading-digit band
[d*ms, (d+1)*ms). Since that width is < 2^64, the only band that can
straddle 2^64 is d == dmax (the largest leading digit that still fits),
and there it straddles at most once, so a single threshold dmax*ms
separates wrapped from non-wrapped values. A leading digit above dmax
always overflows; below dmax always fits. dmax and the threshold derive
from the existing min_safe_u64 table, so no new tables are needed and
dmax*ms cannot itself overflow.
Add a programmatic, self-verifying test for parse_int_string overflow
detection covering bases 2..36, complementing the hand-picked strings
added earlier. Every generated input is cross-checked against an
independent trusted oracle (a plain 64-bit checked multiply-add); on
success the parsed value is also compared exactly and full consumption
of the input is asserted.
Per base it exercises:
- an exact-boundary sweep of the 64 values straddling 2^64
(UINT64_MAX-31 .. 2^64+31), built by walking the digit string;
- UINT64_MAX, 2^64 and the all-max-digit value, each also with
leading zeros;
- random max_digits-length values across every leading digit, with
the heaviest sampling on the lead == dmax band that straddles 2^64,
and full coverage of lead > dmax (the multi-wrap region the naive
min_safe check accepted by mistake);
- max_digits-1 (never overflows) and max_digits+1 (always overflows).
A small signed (int64_t) section checks the exact INT64_MIN/INT64_MAX
limits round-trip and that INT64_MAX+1 / INT64_MIN-1 are rejected in
every base.
Same std::thread split as exhaustive32_midpoint; preserves each test's existing
failure behavior (abort for exhaustive32, stop-flag for exhaustive32_64).
When calling ch_to_digit() with a UTF-16 or UTF-32 code unit, it simply
truncates away any data stored in the non-low byte(s) of the code unit.
It then uses a lookup table to determine whether the low byte
corresponds to an ASCII digit. This is incorrect because as soon as any
bit outside the low byte is set, the number will never correspond to a
ASCII digit anymore.
To fix this, we produce a mask that is all zeroes if any bit outside the
low byte is set in the code unit, all ones otherwise. Anding this mask
with the original code unit forces the table lookup to return the
sentinel value from the zero-index if any high bit was set and causes
the code unit not to be parsed as integer.
This bug was discovered when loading Mastodon posts inside the Ladybird
browser where some of Mastodon's JavaScript would trigger the code path
that erroneously parsed the emoji as integer. It had the visible effect
that some digits inside the posts would get rendered as one of the
emojis that parsed to that digit. For more details see this issue:
https://github.com/LadybirdBrowser/ladybird/issues/6205
The emojis in the test case are simply all the emojis used on Mastodon
that caused the bug. They can be found here:
06803422da/app/javascript/mastodon/features/emoji/emoji_map.json
