Add unsafe example
This commit is contained in:
Timothy Warren
parent
6d65d88b76
commit
6cf7aa9000
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@ -36,6 +36,7 @@
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<cargoProject FILE="$PROJECT_DIR$/gui/Cargo.toml" />
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<cargoProject FILE="$PROJECT_DIR$/blog/Cargo.toml" />
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<cargoProject FILE="$PROJECT_DIR$/pattern_matching/Cargo.toml" />
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<cargoProject FILE="$PROJECT_DIR$/unsafe_blocks/Cargo.toml" />
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</component>
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<component name="ComposerJsonPluginSettings">
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<unboundedVersionInspectionSettings>
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@ -145,6 +145,10 @@
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<sourceFolder url="file://$MODULE_DIR$/pattern_matching/examples" isTestSource="false" />
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<sourceFolder url="file://$MODULE_DIR$/pattern_matching/tests" isTestSource="true" />
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<sourceFolder url="file://$MODULE_DIR$/pattern_matching/benches" isTestSource="true" />
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<sourceFolder url="file://$MODULE_DIR$/unsafe_blocks/src" isTestSource="false" />
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<sourceFolder url="file://$MODULE_DIR$/unsafe_blocks/examples" isTestSource="false" />
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<sourceFolder url="file://$MODULE_DIR$/unsafe_blocks/tests" isTestSource="true" />
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<sourceFolder url="file://$MODULE_DIR$/unsafe_blocks/benches" isTestSource="true" />
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<excludeFolder url="file://$MODULE_DIR$/add/add-one/target" />
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<excludeFolder url="file://$MODULE_DIR$/add/adder/target" />
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<excludeFolder url="file://$MODULE_DIR$/adder/target" />
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@ -179,6 +183,7 @@
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<excludeFolder url="file://$MODULE_DIR$/threads/target" />
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<excludeFolder url="file://$MODULE_DIR$/trait_objects/target" />
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<excludeFolder url="file://$MODULE_DIR$/twelve_days_of_christmas/target" />
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<excludeFolder url="file://$MODULE_DIR$/unsafe_blocks/target" />
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<excludeFolder url="file://$MODULE_DIR$/variables/target" />
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</content>
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<orderEntry type="inheritedJdk" />
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@ -2,6 +2,8 @@
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<project version="4">
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<component name="ChangeListManager">
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<list default="true" id="c8f42924-1cd2-4b1c-bcff-602a3368bb16" name="Default Changelist" comment="">
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<change afterPath="$PROJECT_DIR$/unsafe_blocks/Cargo.toml" afterDir="false" />
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<change afterPath="$PROJECT_DIR$/unsafe_blocks/src/main.rs" afterDir="false" />
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<change beforePath="$PROJECT_DIR$/.idea/misc.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/misc.xml" afterDir="false" />
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<change beforePath="$PROJECT_DIR$/.idea/rust.iml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/rust.iml" afterDir="false" />
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<change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
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@ -15,10 +17,10 @@
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<component name="FileEditorManager">
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<leaf>
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<file pinned="false" current-in-tab="true">
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<entry file="file://$PROJECT_DIR$/pattern_matching/src/main.rs">
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<entry file="file://$PROJECT_DIR$/unsafe_blocks/src/main.rs">
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<provider selected="true" editor-type-id="text-editor">
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<state relative-caret-position="903">
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<caret line="194" column="24" selection-start-line="194" selection-start-column="24" selection-end-line="194" selection-end-column="24" />
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<state relative-caret-position="552">
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<caret line="40" column="56" selection-start-line="40" selection-start-column="56" selection-end-line="40" selection-end-column="56" />
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</state>
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</provider>
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</entry>
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@ -52,7 +54,6 @@
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<component name="IdeDocumentHistory">
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<option name="CHANGED_PATHS">
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<list>
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<option value="$PROJECT_DIR$/rectangles/src/main.rs" />
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<option value="$PROJECT_DIR$/enums/src/main.rs" />
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<option value="$PROJECT_DIR$/modules/src/sound.rs" />
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<option value="$PROJECT_DIR$/modules/src/performance_group.rs" />
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@ -103,6 +104,7 @@
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<option value="$PROJECT_DIR$/blog/src/main.rs" />
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<option value="$PROJECT_DIR$/blog/Cargo.toml" />
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<option value="$PROJECT_DIR$/pattern_matching/src/main.rs" />
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<option value="$PROJECT_DIR$/unsafe_blocks/src/main.rs" />
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</list>
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</option>
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</component>
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@ -112,11 +114,11 @@
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<annotation-enable>false</annotation-enable>
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<other-services-enabled>false</other-services-enabled>
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</component>
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<component name="ProjectFrameBounds">
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<option name="x" value="1680" />
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<option name="y" value="-410" />
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<component name="ProjectFrameBounds" extendedState="6">
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<option name="x" value="1920" />
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<option name="y" value="582" />
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<option name="width" value="1050" />
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<option name="height" value="1657" />
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<option name="height" value="877" />
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</component>
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<component name="ProjectLevelVcsManager" settingsEditedManually="true">
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<ConfirmationsSetting value="1" id="Add" />
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@ -136,12 +138,12 @@
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<path>
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<item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
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<item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
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<item name="pattern_matching" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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<item name="unsafe_blocks" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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</path>
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<path>
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<item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
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<item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
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<item name="pattern_matching" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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<item name="unsafe_blocks" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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<item name="src" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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</path>
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</expand>
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@ -175,7 +177,7 @@
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</component>
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<component name="PropertiesComponent">
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<property name="JavaScriptWeakerCompletionTypeGuess" value="true" />
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<property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1549488475930" />
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<property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1549557641362" />
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<property name="javascript.nodejs.core.library.configured.version" value="7.1.0" />
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<property name="js.eslint.eslintPackage" value="$USER_HOME$/.yarn-config/global/node_modules/.bin/eslint" />
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<property name="js.eslint.nodeInterpreter" value="project" />
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@ -203,7 +205,7 @@
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</list>
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</option>
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</component>
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<component name="RunManager" selected="Cargo Command.Run pattern_matching">
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<component name="RunManager" selected="Cargo Command.Run unsafe_blocks">
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<configuration name="<template>" type="TestNG" default="true" selected="false">
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<option name="MAIN_CLASS_NAME" />
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<option name="VM_PARAMETERS" value="-ea" />
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@ -252,13 +254,13 @@
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<envs />
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<method v="2" />
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</configuration>
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<configuration name="Run twelve_days_of_christmas" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
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<configuration name="Run unsafe_blocks" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
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<option name="channel" value="DEFAULT" />
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<option name="command" value="run --package twelve_days_of_christmas --bin twelve_days_of_christmas" />
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<option name="command" value="run --package unsafe_blocks --bin unsafe_blocks" />
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<option name="allFeatures" value="false" />
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<option name="nocapture" value="false" />
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<option name="backtrace" value="SHORT" />
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<option name="workingDirectory" value="file://$PROJECT_DIR$/twelve_days_of_christmas" />
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<option name="workingDirectory" value="file://$PROJECT_DIR$/unsafe_blocks" />
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<envs />
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<method v="2" />
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</configuration>
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@ -281,11 +283,11 @@
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</configuration>
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<recent_temporary>
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<list>
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<item itemvalue="Cargo Command.Run unsafe_blocks" />
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<item itemvalue="Cargo Command.Run pattern_matching" />
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<item itemvalue="Cargo Command.Run blog" />
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<item itemvalue="Cargo Command.Run gui" />
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<item itemvalue="Cargo Command.Test lib::tests" />
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<item itemvalue="Cargo Command.Run twelve_days_of_christmas" />
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</list>
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</recent_temporary>
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</component>
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@ -322,11 +324,11 @@
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</history-entry>
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</component>
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<component name="ToolWindowManager">
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<frame x="1680" y="-410" width="1050" height="1657" extended-state="6" />
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<frame x="1920" y="-438" width="1080" height="1897" extended-state="6" />
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<editor active="true" />
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<layout>
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<window_info content_ui="combo" id="Project" order="0" sideWeight="0.49586776" visible="true" weight="0.26141885" />
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<window_info content_ui="combo" id="Project" order="0" sideWeight="0.496614" visible="true" weight="0.2540132" />
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<window_info id="Image Layers" order="2" />
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<window_info id="Designer" order="3" />
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<window_info id="Capture Tool" order="4" />
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@ -334,7 +336,7 @@
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<window_info id="Cargo" order="6" sideWeight="0.49791494" weight="0.3286119" />
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<window_info anchor="bottom" id="Message" order="0" />
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<window_info anchor="bottom" id="Find" order="1" weight="0.32979318" />
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<window_info active="true" anchor="bottom" id="Run" order="2" visible="true" weight="0.29696578" />
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<window_info active="true" anchor="bottom" id="Run" order="2" visible="true" weight="0.2571269" />
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<window_info anchor="bottom" id="Debug" order="3" weight="0.4" />
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<window_info anchor="bottom" id="Cvs" order="4" weight="0.25" />
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<window_info anchor="bottom" id="Inspection" order="5" weight="0.4" />
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@ -356,13 +358,6 @@
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<option name="version" value="1" />
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</component>
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<component name="editorHistoryManager">
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<entry file="file://$PROJECT_DIR$/structs/src/main.rs">
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</entry>
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<entry file="file://$PROJECT_DIR$/slices/src/main.rs">
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<provider selected="true" editor-type-id="text-editor">
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<state relative-caret-position="704">
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@ -789,8 +784,15 @@
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</entry>
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<entry file="file://$PROJECT_DIR$/pattern_matching/src/main.rs">
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<provider selected="true" editor-type-id="text-editor">
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</provider>
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</entry>
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<entry file="file://$PROJECT_DIR$/unsafe_blocks/src/main.rs">
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<provider selected="true" editor-type-id="text-editor">
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</provider>
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</entry>
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@ -0,0 +1,7 @@
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[package]
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name = "unsafe_blocks"
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version = "0.1.0"
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authors = ["Timothy Warren <twarren@nabancard.com>"]
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edition = "2018"
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[dependencies]
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@ -0,0 +1,95 @@
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//! Unsafe Example
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//!
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//! In Rust, unsafe means less automated safety, not no safety. It's an
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//! escape hatch for code not normally allowed by the Rust compiler.
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//!
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//! Unsafe code allows the following 4 abilities:
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//!
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//! 1. Dereferencing raw pointers
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//! 2. Calling an unsafe function or method
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//! 3. Acessing/Mutating a mutable static variable (global)
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//! 4. Implementing an unsafe trait
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use std::slice;
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extern "C" {
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fn abs(input: i32) -> i32;
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}
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// Immutable static variable (global) - safe
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static HELLO_WORLD: &str = "Hello, world!";
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// Mutable static variable - unsafe to access or mutate
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static mut COUNTER: u32 = 0;
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fn raw_pointer() {
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let mut num = 5;
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// Casting references to raw pointers
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// Raw pointers can be created in safe code,
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// but can only be dereferenced in unsafe code
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let r1 = &num as *const i32;
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let r2 = &mut num as *mut i32;
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unsafe {
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println!("r1 is: {}", *r1);
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println!("r2 is: {}", *r2);
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}
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}
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/// An unsafe function can only be called within an unsafe block
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/// This is essentially the same as wrapping the entire function in an unsafe block,
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/// as an unsafe block in the function body is redundant
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unsafe fn dangerous() {}
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/// A 'safe' function can wrap unsafe code
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fn split_at_mut(slice: &mut [i32], mid: usize) -> (&mut [i32], &mut [i32]) {
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let len = slice.len();
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let ptr = slice.as_mut_ptr(); // Get the raw pointer of the slice
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assert!(mid <= len);
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unsafe {
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// These slice methods are unsafe because they require a valid pointer.
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// Since the Rust compiler can not verify the safety of the pointers,
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// the calls must be in an unsafe block. The function is still considered
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// safe, though, because the original pointer is valid, and the bounds
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// of the slice are verified with the assert call.
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(
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slice::from_raw_parts_mut(ptr, mid),
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slice::from_raw_parts_mut(ptr.offset(mid as isize), len - mid)
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)
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}
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}
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/// A call to a function from a foreign programming language is considered
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/// unsafe, as rust can not verify the safety of the external code.
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/// While this can be wrapped in a 'safe' function, it is (unfortunately) up to the programmer
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/// to make sure the call is actually safe
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fn c_library_call() {
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unsafe {
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println!("Absolute value of -3 according to C: {}", abs(-3));
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}
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}
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/// Mutable static variables (globals) are unsafe to access
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/// or mutate due to the possibility of data races in multithreaded code
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fn add_to_count(inc: u32) {
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unsafe {
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COUNTER += inc; // Mutating a mutable static variable is unsafe
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}
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}
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fn main() {
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raw_pointer();
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add_to_count(3);
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unsafe {
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dangerous();
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println!("COUNTER: {}", COUNTER); // Accessing a mutable static variable is unsafe
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}
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c_library_call();
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}
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