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Tools/SmartCheck/Solidity/Rules/SOLIDITY_VAR.md

+# Analysis of Smart Contract Security Vulnerabilities and Tools ![](https://img.shields.io/badge/-Live-brightgreen)
+![](https://img.shields.io/badge/Batch-UG21CYS-lightgreen) ![](https://img.shields.io/badge/Batch-PG21CYS-green) ![](https://img.shields.io/badge/Batch-UG22CYS-lightgreen) ![](https://img.shields.io/badge/Batch-PG21CYS-green) ![](https://img.shields.io/badge/Batch-PhD-darkgreen) ![](https://img.shields.io/badge/-B_RIG-darkgreen)<br/>   ![](https://img.shields.io/badge/BlockchainCourse-21CY712-green)  ![](https://img.shields.io/badge/-M.Tech_Dissertation-blue) ![](https://img.shields.io/badge/Focus-Smart_Contract_Security-yellow) <br/>
+![](https://img.shields.io/badge/Blockchain-Ethereum-blue)   <br/> 
+![](https://img.shields.io/badge/Language-Solidity-blue)
+
+## SOLIDITY_VAR
+### Rule Description
+<p>
+    Solidity supports type inference: the type of <code>i</code> in <code>var i = 42;</code> is the smallest integer type sufficient to store the right-hand side value (<code>uint8</code>). Consider a common for-loop pattern:
+</p>
+<pre>
+<code>
+for (var i = 0; i < array.length; i++) { /* ... */ }
+</code>
+</pre>
+<p>
+The type of <code>i</code> is inferred to <code>uint8</code>. If <code>array.length</code> is bigger than 255, an
+overflow will occur. Explicitly define the type when declaring integer variables:
+</p>
+<pre>
+<code>
+for (uint256 i = 0; i < array.length; i++) { /* ... */ }
+</code>
+</pre>
+
+### Solidity-Rules
+
+![](https://img.shields.io/badge/Pattern_ID-d28aa7-gold) ![](https://img.shields.io/badge/Severity-2-brown) 
+
+```
+varDeclaration
+                        [expression//primaryExpression/numberLiteral/decimalNumber]
+```
+
+![](https://img.shields.io/badge/Pattern_ID-f77619-gold) ![](https://img.shields.io/badge/Severity-1-brown) 
+
+```
+varDeclaration[expression/primaryExpression/identifier]
+
+```
+
+### Sample Code
+
+```
+pragma solidity ^0.4.11;
+
+contract SolidityVarZero {
+    function foo1() {
+        // <yes> <report> SOLIDITY_VAR d28aa7
+        for (var i = 0; i < a.length; i ++) { a[i] = i; }
+    }
+    function foo2() {
+        for (uint16 i = 0; i < a.length; i ++) { a[i] = i; }
+    }
+    function foo3() {
+        // <yes> <report> SOLIDITY_VAR f77619
+        var a;
+        // <yes> <report> SOLIDITY_VAR d28aa7
+        var minIdx = 0; /* inferred to uint8 */
+        for (var i = minIdx; i < a.length; i++) { a[i] = i; }
+
+    }
+}
+```
+
+### Abstract Syntax Tree 
+
+[Click Here](https://astexplorer.net/#/gist/6b22697ad5117504fd7c16ac421c39ec/5a9102754f45b2e727eeee27f91e6240b75132b1) to view the AST for the above code. Code generated from AST Explorer using _solidity-parser-antlr-0.4.11_
+
+
+### Code Result
+
+```
+ruleId: SOLIDITY_EXTRA_GAS_IN_LOOPS
+patternId: d3j11j
+severity: 1
+line: 6
+column: 8
+content: for(vari=0;i<a.length;i++){a[i]=i;}
+
+ruleId: SOLIDITY_EXTRA_GAS_IN_LOOPS
+patternId: d3j11j
+severity: 1
+line: 9
+column: 8
+content: for(uint16i=0;i<a.length;i++){a[i]=i;}
+
+ruleId: SOLIDITY_EXTRA_GAS_IN_LOOPS
+patternId: d3j11j
+severity: 1
+line: 16
+column: 8
+content: for(vari=minIdx;i<a.length;i++){a[i]=i;}
+
+ruleId: SOLIDITY_GAS_LIMIT_IN_LOOPS
+patternId: f6f853
+severity: 2
+line: 6
+column: 8
+content: for(vari=0;i<a.length;i++){a[i]=i;}
+
+ruleId: SOLIDITY_GAS_LIMIT_IN_LOOPS
+patternId: f6f853
+severity: 2
+line: 9
+column: 8
+content: for(uint16i=0;i<a.length;i++){a[i]=i;}
+
+ruleId: SOLIDITY_PRAGMAS_VERSION
+patternId: 23fc32
+severity: 1
+line: 1
+column: 16
+content: ^
+
+ruleId: SOLIDITY_VAR
+patternId: d28aa7
+severity: 2
+line: 6
+column: 13
+content: vari=0
+
+ruleId: SOLIDITY_VAR
+patternId: d28aa7
+severity: 2
+line: 15
+column: 8
+content: varminIdx=0
+
+ruleId: SOLIDITY_VAR
+patternId: f77619
+severity: 1
+line: 16
+column: 13
+content: vari=minIdx
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 4
+column: 4
+content: functionfoo1(){for(vari=0;i<a.length;i++){a[i]=i;}}
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 8
+column: 4
+content: functionfoo2(){for(uint16i=0;i<a.length;i++){a[i]=i;}}
+
+ruleId: SOLIDITY_VISIBILITY
+patternId: 910067
+severity: 1
+line: 11
+column: 4
+content: functionfoo3(){vara;varminIdx=0;for(vari=minIdx;i<a.length;i++){a[i]=i;}}
+
+SOLIDITY_VISIBILITY :3
+SOLIDITY_PRAGMAS_VERSION :1
+SOLIDITY_VAR :3
+SOLIDITY_EXTRA_GAS_IN_LOOPS :3
+SOLIDITY_GAS_LIMIT_IN_LOOPS :2
+
+```