[cost] make the size of collection more accurate when modifying in loop

Summary:
Two issues are fixed
1. For this diff, when the condition `curr_langauge_is Java` is removed in some part of the analysis, some c bufferoverrun tests are broken. This is fixed in this diff by inspecting if we are dealing with a `Size` alias referring to an `objc_internal_collection_array`.
2. Previously, when we are modifying mutable array in a loop, e.g. adding element to the array or removing element from the array, we are unable to give an estimable size of the array after exiting the loop. This is now fixed, and the corresponding FPs are resolved.

Reviewed By: skcho

Differential Revision: D23342350

fbshipit-source-id: 200f5261c

infer/src/bufferoverrun/absLoc.ml

@@ -231,6 +231,13 @@ module Loc = struct
         false
 
 
+  let is_objc_collection_internal_array = function
+    | BoField.Field {fn} ->
+        Fieldname.equal fn BoField.objc_collection_internal_array
+    | _ ->
+        false
+
+
   let is_objc_iterator_offset = function
     | BoField.Field {fn} ->
         Fieldname.equal fn BoField.objc_iterator_offset
@@ -362,7 +369,10 @@ module Loc = struct
     | BoField.Prim (Allocsite allocsite) ->
         Allocsite.represents_multiple_values allocsite
     | BoField.Field _ as x
-      when is_c_strlen x || is_java_collection_internal_array x || is_objc_iterator_offset x ->
+      when is_c_strlen x
+           || is_java_collection_internal_array x
+           || is_objc_iterator_offset x
+           || is_objc_collection_internal_array x ->
         false
     | BoField.Field {prefix= l} ->
         represents_multiple_values l

infer/src/bufferoverrun/absLoc.mli

@@ -96,6 +96,8 @@ module Loc : sig
 
   val represents_multiple_values : t -> bool
 
+  val is_objc_collection_internal_array : t -> bool
+
   val append_field : ?typ:Typ.typ -> t -> Fieldname.t -> t
   (** It appends field. [typ] is the type of [fn]. *)
 end

infer/src/bufferoverrun/bufferOverrunDomain.ml

@@ -1115,6 +1115,12 @@ module AliasTargets = struct
           ()
     in
     match iter is_simple_zero x with () -> None | exception Found rhs -> Some rhs
+
+
+  let find_size_alias x =
+    let exception Found of KeyRhs.t in
+    let is_size rhs = function AliasTarget.Size _ -> raise (Found rhs) | _ -> () in
+    match iter is_size x with () -> None | exception Found rhs -> Some rhs
 end
 
 module AliasMap = struct
@@ -1163,13 +1169,21 @@ module AliasMap = struct
    fun loc x -> find (KeyLhs.LocKey loc) x |> AliasTargets.map (AliasTarget.set_java_tmp loc)
 
 
+  let has_objc_collection_size_alias : Loc.t -> t -> bool =
+   fun loc x ->
+    AliasTargets.find_size_alias (find_loc loc x)
+    |> Option.value_map ~default:false ~f:Loc.is_objc_collection_internal_array
+
+
   let load : Ident.t -> Loc.t -> AliasTarget.t -> t -> t =
    fun id loc tgt x ->
     if Loc.is_unknown loc || AliasTarget.is_unknown tgt then x
     else
       let tgts =
         match tgt with
-        | AliasTarget.Simple {i} when IntLit.iszero i && Language.curr_language_is Java ->
+        | AliasTarget.Simple {i}
+          when IntLit.iszero i
+               && (Language.curr_language_is Java || has_objc_collection_size_alias loc x) ->
             find_loc loc x |> AliasTargets.add loc tgt
         | _ ->
             AliasTargets.singleton loc tgt

infer/tests/codetoanalyze/objc/performance/NSMutableArray.m

@@ -23,10 +23,7 @@ void nsmarray_empty_ok_costant() {
   [array insertObject:@1 atIndex:0];
 }
 
-// top cost caused by not able to estimate the
+void nsmarray_add_in_loop_constant() {
-// length of array after adding elements to the
-// array in a loop
-void nsmarray_add_in_loop_constant_FP() {
   NSMutableArray* array = [[NSMutableArray alloc] init];
   for (int i = 0; i < 10; i++) {
     [array addObject:[NSNumber numberWithInt:i]];
@@ -35,7 +32,7 @@ void nsmarray_add_in_loop_constant_FP() {
   }
 }
 
-void nsmarray_add_in_loop_linear_FP(NSUInteger n) {
+void nsmarray_add_in_loop_linear(NSUInteger n) {
   NSMutableArray* array = [[NSMutableArray alloc] init];
   for (int i = 0; i < n; i++) {
     [array addObject:[NSNumber numberWithInt:i]];
@@ -113,7 +110,7 @@ id nsmarray_remove_constant() {
   return array[0];
 }
 
-void nsmarray_remove_in_loop_constant_FP() {
+void nsmarray_remove_in_loop_constant() {
   NSMutableArray* array = [[NSMutableArray alloc] init];
   for (int i = 0; i < 10; i++) {
     [array addObject:[NSNumber numberWithInt:i]];

infer/tests/codetoanalyze/objc/performance/cost-issues.exp

@@ -39,15 +39,15 @@ codetoanalyze/objc/performance/NSDictionary.m, nsdictionary_init_with_dictionary
 codetoanalyze/objc/performance/NSInteger.m, nsinteger_value_linear, 3 + 3 ⋅ integer + 2 ⋅ (1+max(0, integer)),  OnUIThread:false, [{1+max(0, integer)},Loop,{integer},Loop]
 codetoanalyze/objc/performance/NSInteger.m, nsnumber_number_with_int_integer_value_constant, 34,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_all_constant, 23,  OnUIThread:false, []
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_constant_FP, ⊤,  OnUIThread:false, [Unbounded loop,Loop]
+codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_constant, 152,  OnUIThread:false, []
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_linear_FP, ⊤,  OnUIThread:false, [Unbounded loop,Loop]
+codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_linear, 8 + 7 ⋅ n + 3 ⋅ n + 2 ⋅ (n + 1) + 3 ⋅ (n + 1),  OnUIThread:false, [{n + 1},Loop,{n + 1},Loop,{n},Loop,{n},Loop]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_quadratic, 6 + 5 ⋅ n + 8 ⋅ n × m + 2 ⋅ n × (m + 1) + 2 ⋅ (n + 1),  OnUIThread:false, [{n + 1},Loop,{m + 1},Loop,{m},Loop,{n},Loop]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_then_loop_constant, 108,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_empty_ok_costant, 7,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_init_with_capacity_constant_FP, ⊤,  OnUIThread:false, [Unbounded loop,Loop]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_all_linear, 4 + 3 ⋅ array->elements.length.ub + array->elements.length.ub + 3 ⋅ (array->elements.length.ub + 1),  OnUIThread:false, [{array->elements.length.ub + 1},Loop,{array->elements.length.ub},Modeled call to NSArray.removeAllObjects,{array->elements.length.ub},Loop]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_constant, 17,  OnUIThread:false, []
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant_FP, ⊤,  OnUIThread:false, [Unbounded loop,Loop]
+codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant, 182,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_set_in_loop_constant, 51,  OnUIThread:false, []
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_set_linear, 3 + 11 ⋅ array->elements.length.ub + 3 ⋅ (array->elements.length.ub + 1),  OnUIThread:false, [{array->elements.length.ub + 1},Loop,{array->elements.length.ub},Loop]
 codetoanalyze/objc/performance/NSMutableDictionary.m, nsmutabledictionary_set_element_in_loop_linear_FN, 14,  OnUIThread:false, []

infer/tests/codetoanalyze/objc/performance/issues.exp

@@ -2,16 +2,10 @@ codetoanalyze/objc/performance/NSArray.m, nsarray_empty_array_constant, 3, CONDI
 codetoanalyze/objc/performance/NSArray.m, nsarray_init_constant, 3, CONDITION_ALWAYS_FALSE, no_bucket, WARNING, [Here]
 codetoanalyze/objc/performance/NSDictionary.m, nsdictionary_init_with_dictionary_linear_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]
 codetoanalyze/objc/performance/NSDictionary.m, nsdictionary_init_with_dictionary_linear_FP, 2, INTEGER_OVERFLOW_U5, no_bucket, ERROR, [<LHS trace>,Unknown value from: NSDictionary.initWithDictionary:,Binary operation: ([0, +oo] + 1):signed32]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_constant_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_constant_FP, 5, INTEGER_OVERFLOW_L5, no_bucket, ERROR, [<LHS trace>,Array declaration,Binary operation: ([0, +oo] + 1):signed32]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_linear_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_add_in_loop_linear_FP, 5, INTEGER_OVERFLOW_L5, no_bucket, ERROR, [<LHS trace>,Array declaration,Binary operation: ([0, +oo] + 1):signed32]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_init_with_capacity_constant_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_init_with_capacity_constant_FP, 3, INTEGER_OVERFLOW_U5, no_bucket, ERROR, [<LHS trace>,Unknown value from: NSMutableArray.initWithCapacity:,Binary operation: ([0, +oo] + 1):signed32]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_constant, 6, BUFFER_OVERRUN_L3, no_bucket, ERROR, [<Length trace>,Array declaration,Array access: Offset: 0 Size: [0, 2]]
+codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_constant, 6, BUFFER_OVERRUN_L1, no_bucket, ERROR, [<Length trace>,Array declaration,Through,Through,Through,Through,Array access: Offset: 0 Size: 0]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]
+codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant, 6, BUFFER_OVERRUN_L3, no_bucket, ERROR, [<Offset trace>,Set array size,<Length trace>,Assignment,Set array size,Array access: Offset: [0, 9] Size: [1, 10]]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant_FP, 5, INTEGER_OVERFLOW_L5, no_bucket, ERROR, [<LHS trace>,Array declaration,Binary operation: ([0, +oo] + 1):signed32]
-codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_remove_in_loop_constant_FP, 6, BUFFER_OVERRUN_L5, no_bucket, ERROR, [<Offset trace>,Array declaration,<Length trace>,Array declaration,Array access: Offset: [0, +oo] Size: [0, +oo]]
 codetoanalyze/objc/performance/NSMutableArray.m, nsmarray_set_linear, 2, INTEGER_OVERFLOW_U5, no_bucket, ERROR, [<LHS trace>,Unknown value from: NSNumber.intValue,Binary operation: ([-oo, +oo] + 1):signed32]
 codetoanalyze/objc/performance/NSString.m, init_string_constant, 2, CONDITION_ALWAYS_FALSE, no_bucket, WARNING, [Here]
 codetoanalyze/objc/performance/NSString.m, replace_linear_FP, 0, INFINITE_EXECUTION_TIME, no_bucket, ERROR, [Unbounded loop,Loop]