extra qualification error in C++

Question

I have a member function that is defined as follows:

Value JSONDeserializer::ParseValue(TDR type, const json_string& valueString);

When I compile the source, I get:

error: extra qualification 'JSONDeserializer::' on member 'ParseValue'

What is this? How do I remove this error?

Solution 1

This is because you have the following code:

class JSONDeserializer
{
    Value JSONDeserializer::ParseValue(TDR type, const json_string& valueString);
};

This is not valid C++ but Visual Studio seems to accept it. You need to change it to the following code to be able to compile it with a standard compliant compiler (gcc is more compliant to the standard on this point).

class JSONDeserializer
{
    Value ParseValue(TDR type, const json_string& valueString);
};

The error come from the fact that JSONDeserializer::ParseValue is a qualified name (a name with a namespace qualification), and such a name is forbidden as a method name in a class.

Solution 2

This means a class is redundantly mentioned with a class function. Try removing JSONDeserializer::

Solution 3

Are you putting this line inside the class declaration? In that case you should remove the JSONDeserializer::.

Solution 4

A worthy note for readability/maintainability:

You can keep the JSONDeserializer:: qualifier with the definition in your implementation file (*.cpp).

As long as your in-class declaration (as mentioned by others) does not have the qualifier, g++/gcc will play nice.

For example:

In myFile.h:

class JSONDeserializer
{
    Value ParseValue(TDR type, const json_string& valueString);
};

And in myFile.cpp:

Value JSONDeserializer::ParseValue(TDR type, const json_string& valueString)
{
    do_something(type, valueString);
}

When myFile.cpp implements methods from many classes, it helps to know who belongs to who, just by looking at the definition.

Solution 5

I saw this error when my header file was missing closing brackets.

Causing this error:

// Obj.h
class Obj {
public:
    Obj();

Fixing this error:

// Obj.h
class Obj {
public:
    Obj();
};

View more solutions

Comments

[altumano]

Is there any way to make Visual Studio warn about this?

[sharptooth]

@altumano: No, but Cppcheck can do that and also detect non-ASCII characters in identifiers which helps maintain code more portable to gcc.

[altumano]

@sharptooth: thanks, Cppcheck can indeed detect those errors. There is even a Visual Studio plugin for Cppcheck (but it's buggy and do not detect in all files)

[sharptooth]

@altumano: Is it this thing github.com/VioletGiraffe/cppcheck-vs-addin ? If so could you please report the bug - that project is quite alive and there's good chance it will be fixed.

[Len]

Hello from The Future. You can now force MSVC to warn about this, by enabling warning C4596 - docs.microsoft.com/en-us/cpp/error-messages/compiler-warning‌​s/… . I'd go so far as to have it be reported as an error, by adding the compiler switch /we4596

[Zoe stands with Ukraine]

JSONDeserializer:: for the cpp file (or the definition in general) is required. Otherwise, you get an undefined reference. coliru.stacked-crooked.com/a/8f8a0cd3f9db6c94 coliru.stacked-crooked.com/a/6cd1efe94c09d521

[Marvo]

Oh, that's what did it for me. I had the ClazzName:: in my .h file. oops.