unresolved-external

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set

问题 I made a program that has a class with static-only members in it in its own dedicated cpp/h file combo. The probably is that when I try to use these static members in my code, I'm getting "unresolved external" errors at the linker stage. I am remembering to include the h file in my cpp file that is getting the errors. I don't understand. Is this the wrong design approach to take? Basically i want some global objects that are part of a third party API to be available to my whole program, so I

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set

问题 After upgrading Android Studio, a project with no issues started showing issues in the editor. I have lots of Unresolved Reference errors. Anything under the support libraries (support-v4, support-v7). In the screen capture above, anything showing in red isn't resolving and showing as an error. I am also using Lifecycle components and Room database. They seem to have issues as well. Looks like interfaces can be found but classes can't. For example, in one of my classes using Room , android

问题 After upgrading Android Studio, a project with no issues started showing issues in the editor. I have lots of Unresolved Reference errors. Anything under the support libraries (support-v4, support-v7). In the screen capture above, anything showing in red isn't resolving and showing as an error. I am also using Lifecycle components and Room database. They seem to have issues as well. Looks like interfaces can be found but classes can't. For example, in one of my classes using Room , android

问题 After upgrading Android Studio, a project with no issues started showing issues in the editor. I have lots of Unresolved Reference errors. Anything under the support libraries (support-v4, support-v7). In the screen capture above, anything showing in red isn't resolving and showing as an error. I am also using Lifecycle components and Room database. They seem to have issues as well. Looks like interfaces can be found but classes can't. For example, in one of my classes using Room , android

问题 I have linked to the libraries I want to use and added the header files to my project. And the code doesn't show any errors in red squiggle but when I try to run it, it gives me the following error: Error 1 error LNK2001: unresolved external symbol _cvDestroyWindow C:\Users\Jos\documents\visual studio 2010\Projects\ocv\ocv\opcv.obj ocv Error 2 error LNK2001: unresolved external symbol _cvWaitKey C:\Users\Jos\documents\visual studio 2010\Projects\ocv\ocv\opcv.obj ocv Error 3 error LNK2001:

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set

问题 I am compiling a program in Visual Studio 2015, using the FreeType Library. Before, I had used the same project to compile a static library with my own Font class (and many other things), using the library. All was well, and the class worked great. However, I recently changed the project to a Windows application, by changing Properties -> General -> Configuration Type to Application (.exe) . That way, I could make a program and edit the code at the same time, without copying all of the 20

问题 I am sending a simple email in C++. I downloaded a sample C++ program from the below link. http://cboard.cprogramming.com/cplusplus-programming/125655-sending-simple-email-cplusplus.html The sample program seems to hit the following error when it is compiling. Please help me with solution. Error 8 error LNK2019: unresolved external symbol _send_mail referenced in function _wmain Error 9 error LNK2019: unresolved external symbol __imp__recv@16 referenced in function "int __cdecl connect_to