c++11 - C++ Compiler behavior with re-interpreting template parameter constants -


while working on raii-style guard object, ended encoding of guard state in template parameter. seems reasonable if, instance, want recursive / nested guard object that's aware of how many levels deep without space overhead (being pedantic, know) or eliminate runtime overheads. turned academic curiosity though...

something example:

template <unsigned depth> class guard {     unsigned get_depth() const {return depth;} };  guard<2> g2; std::cout << reinterpret_cast< guard<5>* >( &g2 )->get_depth(); // works? crazy? useful?

i cannot life of me think of legitimate reason this, got me thinking if legal c++ , how compiler ought handle (if can @ all) or if it's silly through , through.

i assume because cast target needs known @ compile time, relevant template instantiated cast. has found useful, assuming work , has uses @ all, , if utilized?

the general question guess can reinterpret_cast alter constant template parameters? if type hack (for want of better term) , g2 in case always return 2 (after casting)? or should return 5 (after casting)?

this undefined not because of strict aliasing rule. call get_depth neither reads nor modifies value of object (a template non-type parameter isn't object), doesn't access (as defined in [defns.access]) within meaning of strict aliasing rule.

this controlled instead [class.mfct.non-static]/2:

if non-static member function of class x called object not of type x, or of type derived x, behavior undefined.


Comments

Post a Comment

Popular posts from this blog

asynchronous - C# WinSCP .NET assembly: How to upload multiple files asynchronously -

i using winscp .net assembly uploading files. want upload multiple files asynchronous way. have created method works single upload. public class uploadingdata { private sessionoptions _sessionoptions; private session _session; //connection etc private void onconnected() { foreach (var fileinfo in localfileslist) { var task = task.factory.startnew(() => uploadfilesasync(fileinfo)); } } private async task uploadfilesasync(string file) { string remotefilepath = _session.translatelocalpathtoremote(file, @"/", "/test_data_upload"); var uploading = _session.putfiles(file, remotefilepath, false); //when done await task.run(() => thread.sleep(1000)); } } please suggest me correct way. thanks you can use backgroundworker class this: string[] images = new string[50]; foreach (var path in images) { backgroundworker
Read more

aws api gateway - SerializationException in posting new Records via Dynamodb Proxy Service in API -

i getting "__type": "com.amazon.coral.service#serializationexception" as reply in postman & in test console in api gateway trying post record directly dynamodb using api proxy services.. referring aws article - https://aws.amazon.com/blogs/compute/using-amazon-api-gateway-as-a-proxy-for-dynamodb/ here's mapping { "tablename": "tablenamegoeshere", "item": { "id" : "$context.requestid" "eventname" : "$input.path('$.eventname')", "timestamp" : $input.path('$.timestamp'), "answers": "$util.parsejson($input.path('$.answers'))" } } update: did asked ... , worked if try add array of json objects gives me above same error - here's trying now. please - couldnt find on google well #set($inputroot = $input.path('$')) { "tablename": "answer", "item": {
Read more

asp.net - Problems sending emails from forum -

i have been redesigning site has message board, has been written guy looked after site. it has few problems , written in .asp , uses .mdb files database. you can see whole thing here . feel free post if helps, test thing have set using original files , new database. the basic problem when posts message, supposed email sent them, have posted it. when replies, originator supposed message, replier has been posted. i’d have thought @ point in process there should script/file in postmessage.asp? the postmessage.asp page below. <% option explicit %> <!-- #include virtual="common/adovbs.inc" --> <html> <head> <meta http-equiv="content-type" content="text/html; charset=windows-1252"> <meta name="generator" content="microsoft frontpage 4.0"> <meta name="progid" content="frontpage.editor.document"> <title>new page 2</title> <base target="_self"
Read more