[inferbo][cost] Generalize String models and add models for StringBuilder

Summary:
`String` and `StringBuilder` both implement `CharSequence`. Let's generalize the model for `String` to `CharSequence` wherever possible and add missing models for
- `StringBuilder.append`
- `StringBuilder.toString`

Reviewed By: skcho

Differential Revision: D19558009

fbshipit-source-id: 0dfdb21af

infer/src/bufferoverrun/bufferOverrunModels.ml

@@ -1300,12 +1300,12 @@ module Call = struct
       ; -"memmove" <>$ capt_exp $+ capt_exp $+ capt_exp $+...$--> memcpy
       ; -"memset" <>$ capt_exp $+ any_arg $+ capt_exp $!--> memset
       ; -"strcat" <>$ capt_exp $+ capt_exp $+...$--> strcat
-      ; +PatternMatch.implements_lang "String"
+      ; +PatternMatch.implements_lang "CharSequence"
         &:: "charAt" <>$ capt_exp $+ capt_exp $--> JavaString.charAt
-      ; +PatternMatch.implements_lang "String"
+      ; +PatternMatch.implements_lang "CharSequence"
         &:: "<init>" <>$ capt_exp $+ capt_exp_of_prim_typ char_array
         $--> JavaString.constructor_from_array
-      ; +PatternMatch.implements_lang "String"
+      ; +PatternMatch.implements_lang "CharSequence"
         &:: "<init>" <>$ capt_exp $+ capt_exp $--> JavaString.copy_constructor
       ; +PatternMatch.implements_lang "String"
         &:: "<init>" <>$ capt_exp $--> JavaString.empty_constructor
@@ -1321,6 +1321,9 @@ module Call = struct
         &:: "substring" <>$ capt_exp $+ capt_exp $--> JavaString.substring_no_end
       ; +PatternMatch.implements_lang "CharSequence"
         &:: "substring" <>$ any_arg $+ capt_exp $+ capt_exp $--> JavaString.substring
+      ; +PatternMatch.implements_lang "StringBuilder"
+        &:: "append" <>$ capt_exp $+ capt_exp $+...$--> JavaString.concat
+      ; +PatternMatch.implements_lang "StringBuilder" &:: "toString" <>$ capt_exp $+...$--> id
       ; -"strcpy" <>$ capt_exp $+ capt_exp $+...$--> strcpy
       ; -"strncpy" <>$ capt_exp $+ capt_exp $+ capt_exp $+...$--> strncpy
       ; -"snprintf" <>--> snprintf
@@ -1355,10 +1358,10 @@ module Call = struct
       ; -"std" &:: "basic_string" < capt_typ &+...>:: "length" $ capt_arg $--> StdBasicString.length
       ; -"std" &:: "basic_string" < capt_typ &+...>:: "size" $ capt_arg $--> StdBasicString.length
       ; -"std" &:: "basic_string" &:: "compare" &--> by_value Dom.Val.Itv.top
-      ; +PatternMatch.implements_lang "String"
+      ; +PatternMatch.implements_lang "CharSequence"
         &:: "equals"
-        $ any_arg_of_typ (+PatternMatch.implements_lang "String")
+        $ any_arg_of_typ (+PatternMatch.implements_lang "CharSequence")
-        $+ any_arg_of_typ (+PatternMatch.implements_lang "String")
+        $+ any_arg_of_typ (+PatternMatch.implements_lang "CharSequence")
         $--> by_value Dom.Val.Itv.unknown_bool
       ; +PatternMatch.implements_lang "String"
         &:: "startsWith"

infer/tests/codetoanalyze/java/performance/StringBuilderTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+class StringBuilderTest {
+
+  StringBuilder mId;
+
+  void new_linear(String s) {
+    String str = new StringBuilder(s).toString();
+    for (int i = 0; i < str.length(); i++) {}
+  }
+
+  void new_constant() {
+    String s = new StringBuilder("hello").toString();
+    new_linear(s);
+  }
+
+  void new_capacity_constant() {
+    String s =
+        new StringBuilder(10).toString(); // capacity is irrelevant to underlying size of the string
+    new_linear(s);
+  }
+
+  void append_linear(String s) {
+    String str = new StringBuilder(s).append("me").toString();
+    new_linear(str);
+  }
+}

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

@@ -196,6 +196,8 @@ codetoanalyze/java/performance/MathTest.java, codetoanalyze.java.performance.Mat
 codetoanalyze/java/performance/MathTest.java, codetoanalyze.java.performance.MathTest.max2_symbolic(int,int):void, 0, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 6 + 9 ⋅ (max(x, y)), O((max(x, y))), degree = 1,{max(x, y)},Loop at line 20]
 codetoanalyze/java/performance/MathTest.java, codetoanalyze.java.performance.MathTest.max_symbolic(int[]):void, 0, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 2 + 5 ⋅ arr.length + 4 ⋅ (arr.length + 1), O(arr.length), degree = 1,{arr.length + 1},Loop at line 16,{arr.length},Loop at line 16]
 codetoanalyze/java/performance/PreconditionTest.java, PreconditionTest.checkNotNull_linear(java.util.ArrayList,java.lang.Object):void, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 11 + 8 ⋅ list.length + 3 ⋅ (list.length + 1), O(list.length), degree = 1,{list.length + 1},Loop at line 37,{list.length},Loop at line 37]
+codetoanalyze/java/performance/StringBuilderTest.java, StringBuilderTest.append_linear(java.lang.String):void, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 25 + 5 ⋅ (s.length + 2) + 3 ⋅ (s.length + 3), O(s.length), degree = 1,{s.length + 3},call to void StringBuilderTest.new_linear(String),Loop at line 13,{s.length + 2},call to void StringBuilderTest.new_linear(String),Loop at line 13]
+codetoanalyze/java/performance/StringBuilderTest.java, StringBuilderTest.new_linear(java.lang.String):void, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 9 + 5 ⋅ s.length + 3 ⋅ (s.length + 1), O(s.length), degree = 1,{s.length + 1},Loop at line 13,{s.length},Loop at line 13]
 codetoanalyze/java/performance/StringTest.java, StringTest.byte_array_constructor_linear(byte[]):void, 1, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 6 + 5 ⋅ data.length + 3 ⋅ (data.length + 1), O(data.length), degree = 1,{data.length + 1},Loop at line 55,{data.length},Loop at line 55]
 codetoanalyze/java/performance/StringTest.java, StringTest.index_substring_linear():java.lang.String, 0, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 9 + this.mId.length, O(this.mId.length), degree = 1,{this.mId.length},call to int StringTest.indexof_linear(String),Modeled call to String.indexOf]
 codetoanalyze/java/performance/StringTest.java, StringTest.indexof_from_linear(java.lang.String,int):int, 0, EXPENSIVE_EXECUTION_TIME, no_bucket, ERROR, [with estimated cost 3 + (-j + m.length), O((-j + m.length)), degree = 1,{-j + m.length},Modeled call to String.indexOf]