One of the most frustrating messages which you can get while building your project is a linker error.When I first came across this error , I was told that a bit of code re factoring in my project was required . Later on I realized that this error was being produced due to my unfamiliarity to the C++ Build Process. I have provided a little overview on how the build process works and then a very short example demonstrating how we could tackle such a problem. The solution would be worth the read for both firmware and software developers in the long run. Why ? I'll get to that later , but for now lets get started with the Build Process
Understanding C++ Build Process:
Although the C++ Build Process is fairly complex . Incase you are still interested have a look here . However the following diagram shows the major steps which the IDE takes here in order to build our application from meager .cpp files to a fully functional .exe/dll file .
Creating A Simple Linker Error Scenario :
The following diagram displays a very simple scenario and also includes a method on overcoming the linker error.
Summary:
Only .cpp files are preprocessed and then converted to individual .obj files.Hence In order to solve the problem of “Multiply defined files”. The functions in header files are only prototyped , and the definition of those functions are placed in individual .cpp files. The compiler while preprocessing the CPP file inserts the entire header into that space of the cpp file and since multiple prototype declarations is possible hence the link time error is resolved and since all the functions from the header files are in a single cpp they get registered only once..so no link time errors.
Understanding C++ Build Process:
Although the C++ Build Process is fairly complex . Incase you are still interested have a look here . However the following diagram shows the major steps which the IDE takes here in order to build our application from meager .cpp files to a fully functional .exe/dll file .
Creating A Simple Linker Error Scenario :
The following diagram displays a very simple scenario and also includes a method on overcoming the linker error.
Summary:
Only .cpp files are preprocessed and then converted to individual .obj files.Hence In order to solve the problem of “Multiply defined files”. The functions in header files are only prototyped , and the definition of those functions are placed in individual .cpp files. The compiler while preprocessing the CPP file inserts the entire header into that space of the cpp file and since multiple prototype declarations is possible hence the link time error is resolved and since all the functions from the header files are in a single cpp they get registered only once..so no link time errors.
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