{"id":24297,"date":"2019-05-07T20:58:49","date_gmt":"2019-05-07T20:58:49","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/cppblog\/?p=24297"},"modified":"2019-10-01T21:54:42","modified_gmt":"2019-10-01T21:54:42","slug":"new-code-analysis-quick-fixes-for-uninitialized-memory-c6001-and-use-before-init-c26494-warnings","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cppblog\/new-code-analysis-quick-fixes-for-uninitialized-memory-c6001-and-use-before-init-c26494-warnings\/","title":{"rendered":"New code analysis quick fixes for uninitialized memory (C6001) and use before init (C26494) warnings"},"content":{"rendered":"

In the\u00a0<\/span><\/span>latest Preview release<\/span><\/span><\/a>\u00a0of Visual Studio 2019<\/span><\/span>\u00a0version<\/span><\/span>\u00a016.1<\/span><\/span>, we\u2019ve added two\u00a0<\/span><\/span>quick fixes to the Code Analysis experience<\/span><\/span>\u00a0focused around\u00a0<\/span><\/span>uninitialized<\/span><\/span>\u00a0variable<\/span><\/span>\u00a0check<\/span><\/span>s<\/span><\/span>.<\/span><\/span>\u00a0<\/span><\/span>These quick fixes are available\u00a0<\/span><\/span>via the\u00a0<\/span><\/span>Quick Actions (<\/span><\/span>lightbulb<\/span><\/span>)<\/span><\/span>\u00a0menu on relevant lines, accessed by hovering over the line or squiggle, or by pressing Ctrl<\/span><\/span>+<\/span><\/span>Period.<\/span><\/span><\/p>\n

The<\/span><\/span>\u00a0first<\/span><\/span>\u00a0release of Visual Studio 2019 brought\u00a0<\/span><\/span>in-editor code analysis<\/span><\/span><\/a>\u00a0and various\u00a0<\/span><\/span>C++ productivity improvements<\/span><\/span><\/span><\/a>, including a quick fix for the\u00a0<\/span><\/span>NULL to nullptr rule<\/span><\/span><\/a>\u00a0and others. In implementing further\u00a0<\/span><\/span>code analysis<\/span><\/span>\u00a0<\/span><\/span>quick fixes,\u00a0<\/span><\/span>we are basing de<\/span><\/span>cisions\u00a0<\/span><\/span>on the following criteria:\u00a0<\/span><\/span>1)\u00a0<\/span><\/span>the warning should have a low false positive rate; 2) the warning should be high-impact and have a\u00a0<\/span><\/span>potentially significant<\/span><\/span>\u00a0<\/span><\/span>downside if not corrected; 3) the warning should have a relatively simple fix. Looking at the most feasible warnings,\u00a0<\/span><\/span>Preview<\/span><\/span>\u00a03 provides\u00a0<\/span><\/span>quick fixes for the following<\/span><\/span>:<\/span><\/span><\/p>\n

C6001:\u00a0<\/span>u<\/span>sing uninitialized memory <variable><\/span><\/h3>\n

Visual Studio reports\u00a0<\/span>w<\/span>arning C6001<\/span><\/a>\u00a0<\/span>when an uninitialized local variable is used before being assigned a value,\u00a0<\/span>which can lead<\/span>\u00a0to unpredictable results<\/span>.<\/span>\u00a0<\/span>This warning may be fixed by a<\/span>dd<\/span>ing<\/span>\u00a0empty curly braces so that the variable\/object is\u00a0<\/span>value<\/span>-initialized<\/span>\u00a0(<\/span>will be all zeros<\/span>)<\/span>.<\/span><\/p>\n

\"New<\/p>\n

This warning and corresponding quick fix\u00a0<\/span><\/span>are<\/span><\/span>\u00a0enabled by<\/span><\/span>\u00a0default\u00a0<\/span><\/span>in<\/span><\/span>\u00a0the Microsoft Native Minimum ruleset<\/span><\/span>.<\/span><\/span><\/p>\n

C26494<\/span><\/span>:<\/span><\/span>\u00a0VAR_USE_BEFORE_INIT<\/span><\/span><\/h3>\n

This<\/span><\/span>\u00a0<\/span><\/span>warning<\/span><\/span>\u00a0goes\u00a0<\/span><\/span>hand-in-hand<\/span><\/span>\u00a0with the previous one<\/span><\/span>\u00a0and is fixed in the same way<\/span><\/span>.\u00a0<\/span><\/span>However, while<\/span><\/span>\u00a0warning<\/span><\/span>\u00a0<\/span><\/span>C<\/span><\/span>6001 is generated where the uninitialized variable is used<\/span><\/span>,\u00a0<\/span><\/span>warning C26494<\/span><\/span><\/a>\u00a0<\/span><\/span>shows up\u00a0<\/span><\/span>where the variable is declared.<\/span><\/span><\/p>\n

\"New<\/p>\n

Note that this warning and corresponding quick fix\u00a0<\/span><\/span>are<\/span><\/span>\u00a0not enabled in the default ruleset, but\u00a0<\/span><\/span>rather<\/span><\/span>\u00a0under the\u00a0<\/span><\/span>C++ Core Check Type Rules.<\/span><\/span>\u00a0<\/span><\/span>To\u00a0<\/span><\/span>change rulesets<\/span><\/span><\/a>\u00a0in\u00a0<\/span><\/span>a<\/span><\/span>n<\/span><\/span>\u00a0<\/span><\/span>MSBuild<\/span><\/span>\u00a0project, navigate to Property Pages > Code Analysis > General;\u00a0<\/span><\/span>for projects using CMake, add the\u00a0\"codeAnalysisRuleset\"<\/code> key into\u00a0<\/span><\/span>your\u00a0<\/span><\/span>CMakeSettings.json<\/span><\/span><\/a>\u00a0with the value set to the full path or the filename of a ruleset file.<\/span><\/span><\/p>\n

Send us feedback<\/span>\u00a0<\/span><\/h3>\n

Thank you to everyone\u00a0<\/span>who helps make Visual Studio a better experience for all<\/span>. Your<\/span>\u00a0feedback is critical in ensuring we can deliver the best Code Analysis experience. We\u2019d love for you to download\u202f<\/span>Visual Studio 2019\u00a0<\/span>16.1\u00a0<\/span>Preview\u00a0<\/span>3<\/span><\/a>, give it a try, and let us know how it\u2019s working for you in the comments below or\u00a0<\/span>via email<\/span><\/a>. If you encounter problems or have\u00a0<\/span>suggestion<\/span>s<\/span>,\u00a0<\/span>please\u00a0<\/span>Report A Problem<\/span><\/a>,<\/span>\u00a0or<\/span>\u00a0let us know<\/span>\u00a0via\u202f<\/span>Visual Studio Developer Community<\/span><\/a>. You can also find us on Twitter\u202f<\/span>@<\/span>VisualC<\/span><\/a>.<\/span>\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

In the\u00a0latest Preview release\u00a0of Visual Studio 2019\u00a0version\u00a016.1, we\u2019ve added two\u00a0quick fixes to the Code Analysis experience\u00a0focused around\u00a0uninitialized\u00a0variable\u00a0checks.\u00a0These quick fixes are available\u00a0via the\u00a0Quick Actions (lightbulb)\u00a0menu on relevant lines, accessed by hovering over the line or squiggle, or by pressing Ctrl+Period. The\u00a0first\u00a0release of Visual Studio 2019 brought\u00a0in-editor code analysis\u00a0and various\u00a0C++ productivity improvements, including a quick fix for […]<\/p>\n","protected":false},"author":1079,"featured_media":24299,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[270,230],"tags":[119],"class_list":["post-24297","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-announcement","category-new-feature","tag-code-analysis"],"acf":[],"blog_post_summary":"

In the\u00a0latest Preview release\u00a0of Visual Studio 2019\u00a0version\u00a016.1, we\u2019ve added two\u00a0quick fixes to the Code Analysis experience\u00a0focused around\u00a0uninitialized\u00a0variable\u00a0checks.\u00a0These quick fixes are available\u00a0via the\u00a0Quick Actions (lightbulb)\u00a0menu on relevant lines, accessed by hovering over the line or squiggle, or by pressing Ctrl+Period. The\u00a0first\u00a0release of Visual Studio 2019 brought\u00a0in-editor code analysis\u00a0and various\u00a0C++ productivity improvements, including a quick fix for […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/posts\/24297","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/users\/1079"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/comments?post=24297"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/posts\/24297\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/media\/24299"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/media?parent=24297"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/categories?post=24297"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/cppblog\/wp-json\/wp\/v2\/tags?post=24297"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}