fix out-of-bounds write in DoubleToAscii SHORTEST_SINGLE mode - #311
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fix out-of-bounds write in DoubleToAscii SHORTEST_SINGLE mode#311Ramya-9353 wants to merge 1 commit into
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AddressSanitizer, `-DNDEBUG` build:
==ERROR: AddressSanitizer: heap-buffer-overflow ... WRITE of size 1
#0 DigitGen fast-dtoa.cc:387
google#1 Grisu3 fast-dtoa.cc:579
google#2 FastDtoa fast-dtoa.cc:649
google#3 DoubleToStringConverter::DoubleToAscii double-to-string.cc:427
0 bytes after 10-byte region
Reached from `DoubleToAscii(DBL_MIN, SHORTEST_SINGLE, 0, buf, 10, ...)`, a
conforming call: the header only forbids static_cast<float>(v) being NaN or
+/-Infinity, and a positive double below the smallest float (0 < v < 2^-150)
casts to a finite +0.0f. Grisu3 then takes the shortest-single boundaries from
Single(0.0f).NormalizedBoundaries(), violating its value > 0 precondition, so
DigitGen emits about 20 digits at the double's magnitude into the 10-byte
(kBase10MaximalLengthSingle + 1) buffer.
The existing zero special-case only catches an exact double zero. Extend it so
SHORTEST_SINGLE also emits "0" when the value rounds to a single zero, the way
an actual single zero already renders.
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AddressSanitizer,
-DNDEBUGbuild:Reached from
DoubleToAscii(DBL_MIN, SHORTEST_SINGLE, 0, buf, 10, ...), a conforming call: the header only forbidsstatic_cast<float>(v)being NaN or +/-Infinity, and a positive double below the smallest float (0 < v < 2^-150, e.g.DBL_MINor5e-324) casts to a finite +0.0f. Grisu3 then takes the shortest-single boundaries fromSingle(0.0f).NormalizedBoundaries(), violating its value > 0 precondition, so DigitGen emits about 20 digits at the double magnitude into the 10-byte (kBase10MaximalLengthSingle + 1) buffer.The existing zero special-case only catches an exact double zero. Extend it so SHORTEST_SINGLE also emits "0" when the value rounds to a single zero, the way an actual single zero already renders. Regression case added beside the existing SHORTEST_SINGLE tests in test-dtoa.cc.