Impossible expected class-name before ‘{’ token error to solve

It's a well known issue this开发者_JS百科 damn error

expected class-name before ‘{’ token

Well, despite my hard working and googling, I could not solve this error. Sorry. This is my last shore.

In ui.cpp of a project of mine I do:

#include "wfqueue_proxy_factory.hpp"

OK, this raises this stupid error in my compiler:

In file included from wfqueue_proxy_factory.hpp:29,from ui.cpp:28: wfqueue_manager_proxy.hpp:42: error: expected class-name before ‘{’ token

There are three classes in my project: First

// wfqueue_proxy_factory.hpp
#ifndef _WFQUEUE_PROXY_FACTORY_HPP
#define _WFQUEUE_PROXY_FACTORY_HPP
#include "wfqueue_manager_proxy.hpp"
// ...
class WFQueueProxyFactory {
//...
};
#endif

Second

// wfqueue_manager_proxy.hpp
#ifndef _WFQUEUE_MANAGER_PROXY_HPP
#define _WFQUEUE_MANAGER_PROXY_HPP
#include "workflow.hpp"
#include "wfqueue.hpp"
// ...
class WFQueueManagerProxy : public WFQueue { // This is the problem (line 42)
//...
};
#endif

Third

// wfqueue.hpp
#ifndef _WFQUEUE_HPP
#define _WFQUEUE_HPP
#include "workflow.hpp"
class WFQueue {
// ...
};
#endif

PLEASE PLEASE PLEASE note that I use ; after } of every class, I checked out EVERY header in my project looking for this problem and didn't find any class not followed by ; after its closing bracket. This is valid for workflow.hpp which is a simple class (not deriving from any class, just a plain class).

WFQueue is some sort if interface, I use this pattern with other classes too and they work. WFQueue contains some virtual pure methods... problem should not be here anyway.... I suppose this because I use another "interface" class with other classes and they work fine.

This error disappears if I do this:

// wfqueue_manager_proxy.hpp
#ifndef _WFQUEUE_MANAGER_PROXY_HPP
#define _WFQUEUE_MANAGER_PROXY_HPP
#include "workflow.hpp"
#include "wfqueue.hpp"
// ...
class WFQueueManagerProxy {
//...
};
#endif

Don't really know how to solve this problem... please help me. Thank you

You should run the preprocessor on your code but not compile it, and examine the result. To do this, copy the command which runs the failing compilation, and with most compilers you'd then remove the -o outfile option and add something like -E (see your compiler's documentation for the flag which does preprocessing only).

The compiler will emit (on stdout) the entire translation unit with all #includes and such resolved, so you can clearly see what is missing (just search for the line of code that matches the error line, then look up to see what declarations you find). If it's still not clear what the problem is, write the preprocessed output to a file and try compiling that. You can then tweak the preprocessed source and see what's needed to fix it.

Just a wild guess: Your error says that in

class WFQueueManagerProxy : public WFQueue { // This is the problem (line 42)
//...
};

there must be a class name before {. Therefore I assume that the compiler doesn't know that WFQueue is a class. Are you sure that its definition is included? I mean, maybe in wfqueue.hpp the class is named WfQueue or different in some other way?

The problem might be in misnamed include guards. Try to check if they are really unique per file. It seems that you made it to disable the definition of WFQueue while compiling WFQueueManagerProxy.

It's something it never happened... my god sorry... It seems that my virtual machine backup disk collided with the original one. I run my project on a virtual machine, making the backup, 2 hours ago, probably messed up something... I adjusted it and now the virtual machine can locate the correct folder and the correct files to compile. It was amazing ahaha and obvious, the ols files g++ tried to compile where a previous version filled with mistakes... This was one of that bugs... a guard header repeated. Icecrime was right... despite I looked for repetitions in my files, in the previous version, where I didn't fix this problem, there were some files I pasted and forgot to change guard header. Thank you everyone for your patience and effort. I'm sorry I didn't notice this very strange virtual disk collision in my machine. Thanks again.

Make sure you typed

using namespace omnetpp;

after includes. It solved my problem.