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Yukihiro "Matz" Matsumoto
c6836f494a
mrb_read_float jumped past the *fp assignment via `goto done` when
the exponent had no digits (e.g., "5e", "5e+"). It returned TRUE
without setting *fp, leaving the caller (mrb_str_to_dbl etc.) to
return whatever was on the stack. MSan flagged this; on most runs
the uninitialized read happens to yield 0.0, so the bug is silently
incorrect rather than crashing.
Refactor the finalization (compute res from d, final_p, sign, etc.)
to run once after the optional-exponent block. The malformed-exponent
case now falls through using the mantissa-only `final_p = trunc - dp`,
producing the same result strtod gives for the same input ("5e" -> 5.0
with endp at 'e'). Float("5e") still raises because mrb_str_len_to_dbl
rejects trailing characters under badcheck.
Reported by OSS-Fuzz (MSan).
Co-authored-by: Claude <noreply@anthropic.com>