{"id":96365,"date":"2017-06-08T07:00:00","date_gmt":"2017-06-08T21:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/?p=96365"},"modified":"2019-03-13T01:12:40","modified_gmt":"2019-03-13T08:12:40","slug":"20170608-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20170608-00\/?p=96365","title":{"rendered":"What will GetLastError() return after a failed InitOnceExecuteOnce?"},"content":{"rendered":"

The documentation for Init­Once­Execute­Once<\/code> says <\/p>\n

If the function fails, the return value is zero. To get extended error information, call Get­Last­Error<\/b>. <\/p><\/blockquote>\n

On the other hand, the documentation for the Init­Once­Callback<\/code> says <\/p>\n

If the function returns FALSE<\/b>, the block is not marked as initialized and the call to Init­Once­Execute­Once<\/b> fails. To communicate additional error information, call Set­Last­Error<\/b>. before returning FALSE<\/b>. <\/p><\/blockquote>\n

The second paragraph implies that the Init­Once­Execute­Once<\/code> function does not itself call Get­Last­Error<\/code>, because if it did, then that would wipe out the value set by the callback. Is that really the case? <\/p>\n

Yes, that’s really the case. The remark in the first paragraph about calling Get­Last­Error<\/code> presupposes that your callback uses Get­Last­Error<\/code> to report why it wasn’t able to initialize. <\/p>\n

I agree, however, that the documentation is misleading here. <\/p>\n

But if your callback wants to return status information more complex than a single “success\/failed”, you are probably better served by the synchronous two-phase initialization pattern<\/a>, which makes it a lot easier to return more complex information. You can even use it to throw a C++ exception<\/a>. <\/p>\n","protected":false},"excerpt":{"rendered":"

Whatever you tell it to.<\/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-96365","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"

Whatever you tell it to.<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/96365","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=96365"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/96365\/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=96365"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=96365"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=96365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}