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Bufferoverrun Analysis - small fixes and improvements #1736

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Bufferoverrun Analysis - small fixes and improvements #1736

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31ab607
[inferbo] Fix an ignored case when the upper bounds of offset is +oo,…
sjxer723 Feb 3, 2023
fd0a4e6
[inferbo] Make a more precise upper/lower bound when adding two upper…
sjxer723 Feb 6, 2023
347d391
[inferbo] Initialize locations for arrays within struct typed variables
sjxer723 Feb 24, 2023
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24 changes: 12 additions & 12 deletions infer/src/bufferoverrun/bounds.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -950,25 +950,25 @@ module Bound = struct
let plus_l : weak:bool -> t -> t -> t =
plus_exact ~otherwise:(fun x y ->
match (x, y) with
| MinMax (c1, Plus, Max, d1, _), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Plus, Max, d1, _) ->
Linear (Z.(c1 + d1 + c2), x2)
| MinMax (c1, Minus, Min, d1, _), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Minus, Min, d1, _) ->
Linear (Z.(c1 - d1 + c2), x2)
| MinMax (c1, Plus, Max, d1, x1), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Plus, Max, d1, x1) ->
mk_MinMaxB (Max, (Linear (Z.(c1 + d1 + c2), x2)), (Linear (Z.(c1 + c2), SymLinear.plus (SymLinear.singleton_one x1) x2)))
| MinMax (c1, Minus, Min, d1, x1), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Minus, Min, d1, x1) ->
mk_MinMaxB (Max, (Linear (Z.(c1 - d1 + c2), x2)), (Linear (Z.(c1 + c2), SymLinear.plus (SymLinear.singleton_minus_one x1) x2)))
Comment on lines +953 to +958
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While MinMaxB was introduced to express more complex min/max expressions, it is NOT always a better choice than others. By its complex nature, many operations may easily lose precision on MinMaxB bound, for example, during widening it is more likely to have infinity bounds according to my experience. Therefore, if we want to introduce MinMaxB here for the plus operation, we should evaluate overall precision impacts. Let me check if it is fine for our use cases.

| _, _ ->
MInf )


let plus_u : weak:bool -> t -> t -> t =
plus_exact ~otherwise:(fun x y ->
match (x, y) with
| MinMax (c1, Plus, Min, d1, _), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Plus, Min, d1, _) ->
Linear (Z.(c1 + d1 + c2), x2)
| MinMax (c1, Minus, Max, d1, _), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Minus, Max, d1, _) ->
Linear (Z.(c1 - d1 + c2), x2)
| MinMax (c1, Plus, Min, d1, x1), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Plus, Min, d1, x1) ->
mk_MinMaxB (Min, (Linear (Z.(c1 + d1 + c2), x2)), (Linear (Z.(c1 + c2), SymLinear.plus (SymLinear.singleton_one x1) x2)))
| MinMax (c1, Minus, Max, d1, x1), Linear (c2, x2)
| Linear (c2, x2), MinMax (c1, Minus, Max, d1, x1) ->
mk_MinMaxB (Min, (Linear (Z.(c1 - d1 + c2), x2)), (Linear (Z.(c1 + c2), SymLinear.plus (SymLinear.singleton_minus_one x1) x2)))
| _, _ ->
PInf )

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