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Fix undefined behavior in CheckBitsFit bit-shift on size_t

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Ben Gertzfield
2016-04-29 12:57:48 -07:00
parent 77742a3fba
commit 3400727fff
2 changed files with 38 additions and 7 deletions
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17
src/idl_parser.cpp
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@@ -69,13 +69,16 @@ inline CheckedError NoError() { return CheckedError(false); }
// Ensure that integer values we parse fit inside the declared integer type.
CheckedError Parser::CheckBitsFit(int64_t val, size_t bits) {
// Bits we allow to be used.
auto mask = static_cast<int64_t>((1ull << bits) - 1);
if (bits < 64 &&
(val & ~mask) != 0 && // Positive or unsigned.
(val | mask) != -1) // Negative.
return Error("constant does not fit in a " + NumToString(bits) +
"-bit field");
// Left-shifting a 64-bit value by 64 bits or more is undefined
// behavior (C99 6.5.7), so check *before* we shift.
if (bits < 64) {
// Bits we allow to be used.
auto mask = static_cast<int64_t>((1ull << bits) - 1);
if ((val & ~mask) != 0 && // Positive or unsigned.
(val | mask) != -1) // Negative.
return Error("constant does not fit in a " + NumToString(bits) +
"-bit field");
}
return NoError();
}