What does "void-value is not ignored" error mean and how to remove it?

Question

I try to compile the following code:

#include <cppunit/extensions/HelperMacros.h>
#include "tested.h"

class TestTested : public CppUnit::TestFixture
{
        CPPUNIT_TEST_SUITE(TestTested);
        CPPUNIT_TEST(check_value);
        CPPUNIT_TEST_SUITE_END();

        public:
                void check_value();
};

CPPUNIT_TEST_SUITE_REGISTRATION(TestTested);

void TestTested::check_value() {
        tested t(3);
        int expected_val = t.getValue(); // <----- Line 18.
        CPPUNIT_ASSERT_EQUAL(7, expected_val);
}

As a result I get:

testing.cpp:18:32: Error: void-value is not ignored where it should be

EDDIT

To make the example complete I post the code of the tested.h and tested.cpp:

tested.h

#include <iostream>
using namespace std;

class tested {
    private:
        int x;
    public:
        tested(int int_x);
        void getValue();
};

tested.cpp

#include <iostream>
using namespace std;

tested::tested(int x_inp) {
    x = x_inp;
}

int tested::getValue() {
    return x;
}

Where is line-18 and what is the value of CPPUNIT ... \macros? — iammilind, Apr 18 '13 at 09:06
Which is line 18? Anyway, the error probably suggest you're assigning somwhere the result of calling a function which returns `void`. — Angew is no longer proud of SO, Apr 18 '13 at 09:07
@iammilind, I have changed the code to indicate where the line 18 is. I do not know what the value of CPPUNIT is. — Roman, Apr 18 '13 at 09:10
`void getValue();` How do you expect to assign this to an `int`? This declaration doesn't match the actual definition. — BoBTFish, Apr 18 '13 at 09:13
@kaitian, I have extended my question by putting their all the code that is relevant. — Roman, Apr 18 '13 at 09:13
in tested.h, you decleare "void getValue();", you can replace it with "int getValue();" — kaitian521, Apr 18 '13 at 09:16
Perhaps it is time to pick up a [good book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) or two. You are sure to learn faster that way than by simple trial and error. — juanchopanza, Apr 18 '13 at 09:44

score 4 · Accepted Answer · edited Apr 18 '13 at 09:17

4

you declare void getValue(); in the class tested.. change to int getValue();.

edited Apr 18 '13 at 09:17

BoBTFish

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answered Apr 18 '13 at 09:13

UmNyobe

22,539
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score 1 · Answer 2 · answered Apr 18 '13 at 09:19

1

A void function cannot return a value. You are getting a value of int from the API getValue(), hence it should return an int.

answered Apr 18 '13 at 09:19

bhuwansahni

1,834
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score 1 · Answer 3 · answered Apr 18 '13 at 09:20

Your class definition doesn't match the implementation:

In your header you've declared it in the following way (as an aside, you might want to look into some naming conventions).

class tested {
    private:
        int x;
    public:
        tested(int int_x);
        void getValue();
};

You've declared getValue() as void, i.e no return. Doesn't make much sense for a getter to return nothing, does it?

However, in the .cpp file you've implemented getValue() like so:

int tested::getValue() {
    return x;
}

You need to update the getValue() method signature in the header type so that its return type matches the implementation (int).

What does "void-value is not ignored" error mean and how to remove it?

3 Answers3