Fix UB in random generator #4588
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ephphatha
reviewed
May 17, 2022
Source/engine/random.cpp
Outdated
| @@ -29,7 +29,8 @@ uint32_t GetLCGEngineState() | |||
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| int32_t GetRndSeed() | |||
| { | |||
| return abs(static_cast<int32_t>(sglGameSeed)); | |||
| const int32_t seed = static_cast<int32_t>(sglGameSeed); | |||
| return seed == -2147483648 ? -2147483648 : abs(seed); | |||
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Suggested change
| return seed == -2147483648 ? -2147483648 : abs(seed); | |
| return seed == std::numeric_limits<int32_t>::min() ? std::numeric_limits<int32_t>::min() : abs(seed); |
abs(INT_MIN) is undefined behavior, so process this case without calling abs()
AJenbo
approved these changes
May 18, 2022
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abs(INT_MIN)is undefined behavior, so process this case without callingabs()This problem manifestates itself on FreeBSD with clang 11.0 by breaking
QuestTest.SinglePlayerBadPoolsandRandomTest.ShiftModDistributionSignCarry