c++ - Single template instantiation for separate objects -


consider following:

/* t.h */ template <class t> void too() {     std::cout << "  template: " << typeid(t).name()               << " size: " << sizeof(t) << std::endl; } 
/* a.h */ extern void fooa(); 
/* a.cpp */ struct local {     int a[2]; }  void fooa() {     local l;     std::cout << "<foo a>:\n" << "  real: " << typeid(l).name()               << " size: " << sizeof(l) << std::endl;     too<local>(); } 
/* b.h */ extern void foob(); 
/* b.cpp */ struct local {     int a[4]; };  void foob() {     local l;     std::cout << "<foo b>:\n" << "  real: " << typeid(l).name() \               << " size: " << sizeof(l) << std::endl;     too<local>(); } 
/* main.cpp */ int main() {     fooa();     foob();     return 0; }

compiling , running results in:

<foo a>:   real: 5local size: 8   template: 5local size: 8 <foo b>:   real: 5local size: 16   template: 5local size: 8

which means single template instantiation used both template calls. notably -- first one. while possible workaround 'feature' defining too() 

template <class t, size_t s = sizeof(t)> too();

i wanted know there more generic approaches problem? since above code still fail if 2 calling structures of same size.

edit:

specifically problem lies in fact, can not change files , b. may not introduce anonymous namespaces them. there template side solutions? hence second template parameter.

your program violates odr (one definition rule) containing 2 definitions of struct local. means it's ill-formed , has undefined behaviour, can happen.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

node.js - Getting the socket id,user id pair of a logged in user(s) -

i have web application done using node js , in it,i have authentication system requires users log in before can access pages. have 2 pages,the homepage , updates page. from read docs,a new socket id issued when user opens tab in browser. me being admin,i know socket id of logged in user , more so,the socket id,logged in user id pair logged in users. what method can use socket id,logged in user id pair make sure broadcast realtime info users online?.
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua
Read more