{"id":14893,"date":"2010-02-18T07:00:00","date_gmt":"2010-02-18T07:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2010\/02\/18\/dont-forget-to-double-null-terminate-those-strings-you-pass-to-shfileoperation\/"},"modified":"2010-02-18T07:00:00","modified_gmt":"2010-02-18T07:00:00","slug":"dont-forget-to-double-null-terminate-those-strings-you-pass-to-shfileoperation","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20100218-00\/?p=14893","title":{"rendered":"Don't forget to double-null-terminate those strings you pass to SHFileOperation"},"content":{"rendered":"

\nAbout once every two months for the past six months\n(I stopped checking further back),\nsomebody reports a problem with the\nSHFileOperation<\/code> function.\nOften, they don’t include very much information at all.\nThey just say, “I call the function and it doesn’t work.”\nHere’s an example:\n<\/p>\n

\n

\nI’m hitting a problem with SHFileOperation<\/code>\nwhen using it to frob files in the gonzo directory\nwhen the user’s SID ends in an odd number.\n<\/p>\n

\n    \/\/\n    \/\/ Delete the file.\n    \/\/ szDeletePath contains the full path to the file.\n    \/\/\n    shFileOp.hwnd = NULL;\n    shFileOp.wFunc = FO_DELETE;\n    shFileOp.pFrom = szDeletePath;\n    shFileOp.pTo = NULL;\n    shFileOp.fFlags = FOF_NO_UI;\n    iRet = SHFileOperation( &shFileOp );\n<\/pre>\n
\nThe function returns file not found, but the file\nis definitely there.\n<\/p>\n<\/blockquote>\n
\nIf you read the variable names carefully, you can see the problem.\n<\/p>\n
\nThe pFrom<\/code> and pTo<\/code> members of the\nSHFILEOPSTRUCT<\/code> structure are\n\ndouble-null-terminated strings<\/a>.\n(There’s even a callout box for this in the MSDN documentation.)\nBut a variable named szDeletePath<\/code> is probably\na single-null-terminated string.\n(The name for a double-null-terminated string would be\nszzDeletePath<\/code>.)\n<\/p>\n
\nMy psychic powers tell me that\nszDeletePath<\/code> is not double-null-terminated.\n<\/p><\/blockquote>\n
\nSo far, my psychic powers haven’t failed.\n<\/p>\n
\nNow, you might say that the fact that people make this mistake\nso often is a sign that the function is flawed.\nAnd if the function were designed today, I would agree with you.\nBut this function in its public form is over fifteen years old\n(and in its private form, is around 20 years old),\nand back in those days,\n\nprogrammers were assumed to have the time to understand the subtleties\nof what they were doing<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
About once every two months for the past six months (I stopped checking further back), somebody reports a problem with the SHFileOperation function. Often, they don’t include very much information at all. They just say, “I call the function and it doesn’t work.” Here’s an example: I’m hitting a problem with SHFileOperation when using it […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-14893","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
About once every two months for the past six months (I stopped checking further back), somebody reports a problem with the SHFileOperation function. Often, they don’t include very much information at all. They just say, “I call the function and it doesn’t work.” Here’s an example: I’m hitting a problem with SHFileOperation when using it […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/14893","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=14893"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/14893\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=14893"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=14893"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=14893"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}