{"id":27313,"date":"2007-04-10T10:00:00","date_gmt":"2007-04-10T10:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2007\/04\/10\/what-is-the-default-version-of-a-header-file\/"},"modified":"2007-04-10T10:00:00","modified_gmt":"2007-04-10T10:00:00","slug":"what-is-the-default-version-of-a-header-file","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20070410-00\/?p=27313","title":{"rendered":"What is the default version of a header file?"},"content":{"rendered":"

\nThe general rule with Windows header files is that if you don’t\nspecify which version of the header file you want,\nyou get the latest version.\nFor example, if you have the Windows XP Platform SDK header files\nand you #include <windows.h><\/code>,\nyou’re going to get the Windows XP function prototypes,\nthe Windows XP structures, the\nthe Windows XP flags, all that stuff.\nAnd unless you’re careful,\nthe program you get as a result will most likely run only\non Windows XP.\n<\/p>\n

\nIf you call a function that is new for Windows XP,\nthen your program won’t run on earlier versions of Windows\n\nbecause the import can’t be resolved<\/a>.†\n<\/p>\n

\nIf you use a structure that changed for Windows XP,\nthen your program won’t run on earlier versions of Windows\n\nbecause the structure size will be wrong<\/a>.\n<\/p>\n

\nEven if the structure size didn’t change, using a flag\nthat was introduced in Windows XP\nwill create difficulties for your program when run\non earlier versions of Windows\nbecause those earlier versions don’t support the flag you’re passing.\nDepending on how the function in question was written,\nit may ignore the “flag from the future” or it may reject it as invalid.\n<\/p>\n

\nIf you want your program to run on older versions of Windows,\nyou have a few options.\nFirst, you can explicitly “downgrade” your header file by\ndefining an appropriate symbol or symbols before including\nthe windows.h<\/code> header file.\n<\/p>\n

\n#define WINVER         0x0400\n#define _WIN32_WINNT   0x0400\n#define _WIN32_WINDOWS 0x0400\n#define _WIN32_IE      0x0400\n#include <windows.h>\n#include <commctrl.h>\n#include <shlobj.h>\n...\n<\/pre>\n
\nOh yuck, now we have the messy world of\n“So what’s the difference between\n_WIN32_WINNT<\/code>,\n_WIN32_WINDOWS<\/code>,\n_WIN32_IE<\/code>, and\nWINVER<\/code>?”\nWe’ll pick up this topic next time,\nbut you’re not going to like the answer.\n<\/p>\n
\nNitpicker’s corner<\/b>\n<\/p>\n
\n†That statement is from the operating system’s‡ point of view.\nYou can of course use techniques like\nVisual Studio linker’s delay-load feature to avoid creating an import\ndependency, but that’s outside the operating system.‡\n<\/p>\n
\n‡s\/operating system\/Windows operating system\/<\/p>\n","protected":false},"excerpt":{"rendered":"
The general rule with Windows header files is that if you don’t specify which version of the header file you want, you get the latest version. For example, if you have the Windows XP Platform SDK header files and you #include <windows.h>, you’re going to get the Windows XP function prototypes, the Windows XP structures, the the Windows XP […]<\/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-27313","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
The general rule with Windows header files is that if you don’t specify which version of the header file you want, you get the latest version. For example, if you have the Windows XP Platform SDK header files and you #include <windows.h>, you’re going to get the Windows XP function prototypes, the Windows XP structures, the the Windows XP […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/27313","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=27313"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/27313\/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=27313"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=27313"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=27313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}