This was another day of no runtime bugs. Instead of a picture, I’ll describe a specific(ish) case of using the compiler to catch all uses of a particular pattern in the code.<\/p>\n
class Foo {};\r\n\r\n\/\/ Bar is one of many classes that inherit from Foo\r\nclass Bar : public Foo {};\r\n\r\n\/\/ Baz is one of many classes that inherit from Bar\r\nclass Baz : public Bar {};\r\n\r\nDECLARE_EXTRA_STUFF_FOR_CLASS(Baz);<\/pre>\nSo we have something like the above. The DECLARE_EXTRA_STUFF_FOR_CLASS()<\/strong> macro is used for some but not all classes that inherit directly or indirectly from Foo<\/strong>.<\/span><\/p>\nThere have recently been changes within a system that means that DECLARE_EXTRA_STUFF_FOR_CLASS()<\/strong> is now never needed for any class that inherits from Bar<\/strong> — but it is not invalid for it to remain used in the codebase. Anything that makes use of the EXTRA_STUFF<\/strong> that the macro provides will still work, it’s just extra unneeded code which I’d like to clean up.<\/p>\nI could audit this by hand — find every class inheriting from Bar<\/strong>, check to see if there’s a macro definition for that class somewhere and perform the subsequent clean up, but I’m lazier than that.<\/p>\nI could write a script that finds classes that inherit from Bar<\/strong>, and then search for that class name with the macro, but that also seems like to much work. (A simple regex sweep through the codebase won’t trivially identify class Asd : public Baz {}<\/strong> as inheriting from Bar<\/strong>). I’m lazier than this.<\/p>\nWhat I can do is break the code expanded by the macro if it is passed a subclass of Bar<\/strong>. To do that, I can do something like the following:<\/p>\nclass Foo { public: static void Foo(){}<\/strong> };\r\nclass Bar : public Foo { private: static void Foo();<\/strong> };\r\n\/\/ Add a line to the macro...\r\nDECLARE_EXTRA_STUFF_FOR_CLASS(class_name) \\\r\n\u00a0 \u00a0 extra_stuff; \\\r\n\u00a0 \u00a0 class_name::Foo(); \\<\/strong>\r\n\u00a0 \u00a0 more_extra_stuff<\/pre>\nDone. Anywhere where the macro is invoked for a class inheriting from Bar<\/strong> will trigger a compile error. Walk through the errors, delete calls to that macro, rewrite (i.e. delete) code as necessary.<\/p>\nEnd result: less code. I count that as a win.<\/p>\n
(In my specific case, I made an already existing public method declared in Foo<\/strong> private in Bar<\/strong> because there is no need to call it from or for classes in that part of the hierarchy. This has the added advantage of not polluting the list of Foo<\/strong>‘s members with no functionality of the class. Additionally, I didn’t call the function within the macro but instead took it’s address.)<\/p>\n","protected":false},"excerpt":{"rendered":"This was another day of no runtime bugs. Instead of a picture, I’ll describe a specific(ish) case of using the compiler to catch all uses of a particular pattern in the code. class Foo {}; \/\/ Bar is one of many classes that inherit from Foo class Bar : public Foo {}; \/\/ Baz is … Continue reading “Compiler-assisted code cleaning, Thursday 2013-03-28”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[26],"tags":[],"_links":{"self":[{"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/posts\/1197"}],"collection":[{"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1197"}],"version-history":[{"count":6,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/posts\/1197\/revisions"}],"predecessor-version":[{"id":1244,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=\/wp\/v2\/posts\/1197\/revisions\/1244"}],"wp:attachment":[{"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1197"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1197"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/brnz.org\/hbr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1197"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}