c++ - symbol not found AKA undefined symbol -

-

most of people work on unix face irritating error often. , times take less time solve , take hell lot of time.

even faced regularly , need document or article regarding specific error in c/c++

what cases there might symbol not found/undefined symbol error.

could me know cases?

the error not related unix/windows/any other os, rather languages themselves. rather simple diagnose information compilers provide. tell symbol missing , being used. main reasons symbol missing are:

  • you have declared never defined it
  • you have defined it, did not add compiled symbol (object file/library) linker
  • it external , forgot link library, or linking invalid version, or in wrong order.

the first 1 little trickier if intended define symbol did not match declaration (declared void foo( int, double );, defined void foo( double, int ). other cases, compiler tell exact signature looking for, make sure have defined that symbol, , not close or similar, particular corner case can if using different calling conventions in declaration , definition, similar in code.

in case of libraries external code complexity in identifying library needs linked symbol added, , comes documentation of lib. beware static libraries order of libs in linker command line affects result.

to in finding symbols defined can use nm (gcc, common among unix systems). can run nm against object files/libs linking , search symbol linker complaining about. in cases order makes difference (i.e. symbol there, linker skipped it).

at runtime (thanks matthieu m. pointing out) might have similar issues dynamic libraries, if wrong version of library found in ld_library_path might end library not have required symbol.


Comments

Post a Comment

Popular posts from this blog

objective c - Change font of selected text in UITextView -

-
can suggest me how change font of selected text in uitextview.i cannot use uiwebview since have edit text. have seen pages app.how possible in app. see formatting text within uilabel differently . since need editing, should @ javascript-based editors such ckeditor or tinymce . highly recommend wwdc 2011 video session 511: "rich text editing in safari on ios."
Read more

php - Accessing POST data in Facebook cavas app -

-
so i've got simple form in canvas / iframe facebook app, , i'm trying pass along values post. reading on s.o. , fb's latest docs, understand it, data send via post form can accessed on receiving end $_request object. i read on thread on s.o. in order post forms work need pass along input named "signed_request" value current signed_request (i have signed request working ok otherwise...all login , authentication stuff working fine). isnt mentioned anywhere in official fb docs. so problem comes in $_request object signed request, , bunch of other session stuff. form inputs found. the way can read them set method of form "request" isn't real form method. takes of inputs , sends them args in url. horrible. here's sample page canvas app form i'm using try debug (leaving out authentication stuff): <form enctype="application/x-www-form-urlencoded" method="post" target="_top" id="my_form" action=...
Read more

c# - Getting control value when switching a view as part of a multiview -

-
i have following code in aspx page: <asp:button id="display_button" runat="server" text="display" onclick="button1_click" /> &nbsp; <asp:button id="edit_button" runat="server" text="edit" onclick="button2_click" /> &nbsp; <asp:button id="save_button" runat="server" text="save" onclick="button3_click" visible="false" /> &nbsp; <asp:multiview id="multiview1" runat="server" activeviewindex="0"> <asp:view id="view1" runat="server"> <asp:formview id="view_program" runat="server"> <itemtemplate> <%# eval("status").tostring().trim() %> </itemtemplate> </asp:formview> </asp:view> <asp:view id="view2" runat="server"> ...
Read more