{"id":21473,"date":"2008-07-25T10:00:00","date_gmt":"2008-07-25T10:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2008\/07\/25\/simulating-a-drop-part-two\/"},"modified":"2008-07-25T10:00:00","modified_gmt":"2008-07-25T10:00:00","slug":"simulating-a-drop-part-two","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20080725-00\/?p=21473","title":{"rendered":"Simulating a drop, part two"},"content":{"rendered":"

\nLast time, we wrote a tiny program to simulate dropping a file\non another file,\nbut we discovered that it didn’t work for dropping a file\nonto\nMail Recipient.MAPIMail<\/CODE>.\nThe reason, as you no doubt instantly recognized,\nis that the MAPIMail<\/CODE> handler creates a worker thread,\nand we’re exiting the process before the worker thread has finished\nits work.\n<\/P>\n

\nAnd as you no doubt know by now, the solution is to use the\nSHSetInstanceExplorer<\/CODE> function.\nLet’s bring back\n\nthe ProcessReference<\/CODE> class<\/A>\nand use it to solve our process lifetime problem.\n<\/P>\n

\nint __cdecl wmain(int argc, WCHAR **argv)\n{\n ProcessReference ref;<\/FONT><\/I>\n …\n<\/PRE>\n
\nCompile this program and run it with the command line\n<\/P>\n
\nfakedrop c:\\autoexec.bat “%USERPROFILE%\\SendTo\\Mail Recipient.MAPIMail”\n<\/PRE>\n
\nto watch our process reference save the day.\n<\/P>\n
\nOh wait, it didn’t help. What’s going on?\n<\/P>\n
\nRun this under the debugger and you’ll see an interesting exception:\n<\/P>\n
\n(918.110): Unknown exception – code 80010012 (first chance)\n<\/PRE>\n
\nA little hunting through winerror.h<\/CODE> reveals what\nthis exception means:\n<\/P>\n
\n\/\/\n\/\/ MessageId: RPC_E_SERVER_DIED_DNE\n\/\/\n\/\/ MessageText:\n\/\/\n\/\/  The callee (server [not server application]) is not available and\n\/\/  disappeared; all connections are invalid. The call did not execute.\n\/\/\n#define RPC_E_SERVER_DIED_DNE            _HRESULT_TYPEDEF_(0x80010012L)\n<\/PRE>\n
\nHuh? What’s this RPC stuff?\nOh wait, COM uses RPC.\nThat should be a clue.\n<\/P>\n
\nNotice that our ProcessReference<\/CODE>‘s destructor\nruns after we have already uninitialized COM.\nWhen we invoked the IDropTarget::Drop<\/CODE> method on the\nMAPIMail<\/CODE> drop target,\nit kicked off a background thread to do the work,\nand in order to access the parameters from the background thread,\nit had to do a bit of marshalling,\nwith the help of the functions with ridiculously long names\nCoMarshalInterThreadInterfaceInStream<\/CODE>\nand the only slightly less ridiculous\nCoGetInterfaceAndReleaseStream<\/CODE>.\nBut since we tear down COM immediately,\nwhen the background thread gets around to asking,\n“Okay, and what was that file name?”\nthe thread that has the answer (the main thread) has already\nshut down COM.\nHence the “server died” error.\n<\/P>\n
\nTo fix this, we need to fix the scope of the process reference\nobject:\n<\/P>\n
\n if (argc == 3 && SUCCEEDED(CoInitialize(NULL))) {\n  ProcessReference ref;<\/FONT><\/I>\n  …\n<\/PRE>\n
\nCompile this program and run it with the same command line and…\nit still doesn’t work!\nBut this time you definitely know why:\n\nThe destructor is running at the wrong time<\/A>.\n<\/P>\n
\nI leave it as an exercise to fix the destructor timing problem.\nTo see whether you got it right, run the fakedrop<\/CODE>\ncommand line again.\nWhen you successfully get an email message, then you know you’ve got it.\n<\/P><\/p>\n","protected":false},"excerpt":{"rendered":"
Last time, we wrote a tiny program to simulate dropping a file on another file, but we discovered that it didn’t work for dropping a file onto Mail Recipient.MAPIMail. The reason, as you no doubt instantly recognized, is that the MAPIMail handler creates a worker thread, and we’re exiting the process before the worker thread […]<\/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-21473","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
Last time, we wrote a tiny program to simulate dropping a file on another file, but we discovered that it didn’t work for dropping a file onto Mail Recipient.MAPIMail. The reason, as you no doubt instantly recognized, is that the MAPIMail handler creates a worker thread, and we’re exiting the process before the worker thread […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/21473","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=21473"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/21473\/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=21473"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=21473"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=21473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}