C ++中无法解析的外部符号

Question

I have defined a global variable in a c++ file. eg: bool _variable =1;

Now i use this variable in other c++ file using : extern bool _variable .

But i am getting the error error LNK2001: unresolved external symbol "bool _variable" (?_variable@@3_NA) .

How can i resolve this error??

Answer 1

It means the linker cannot find the definition of such variable.

• Are you sure you wrote it in the same way anywhere?

• Are you sure the c++ file containing the definition gets compiled and linked with the others when you're getting such error?

• Are you sure the namespace where such variable is defined is the same?

Answer 2

也许您忘记了将具有定义变量的文件包含到项目中（假设您使用的是VS）。