c++11 'noexcept' keyword and mocking those functions.

[Alex Shaver]

If a function has 'noexcept' keyword, I don't know if I can mock it. The initial compiling (gcc or clang) complains:

Mock_Foo.h:10:24: error: exception specification of overriding function is more lax than base version

MOCK_CONST_METHOD0(value, int());

                   ^

/gmock-svn/include/gmock/gmock-generated-function-mockers.h:687:62: note: expanded from macro 'MOCK_CONST_METHOD0'

#define MOCK_CONST_METHOD0(m, ...) GMOCK_METHOD0_(, const, , m, __VA_ARGS__)

                                                             ^

/gmock-svn/include/gmock/gmock-generated-function-mockers.h:357:37: note: expanded from macro 'GMOCK_METHOD0_'

GMOCK_RESULT_(tn, __VA_ARGS__) ct Method( \

                                  ^

Foo.h:10:17: note: overridden virtual function is here

virtual int value() const noexcept{ return _value; }

            ^

Here's the sample code used to generate:

Foo.h:

class Foo{
public:
  Foo();
  ~Foo();


  virtual int value() const noexcept{ return _value; }
  virtual void setValue(const int value){ _value = value; }


private:
  int _value;
};


class Bar{
public:
  Bar(Foo* foo) : _foo{foo}{}
  void doStuff(){
    _foo->value();
   }
private:
  Foo* _foo;
 };

Mock_Foo.h
#include "Foo.h"
#include "gmock/gmock.h"
class Mock_Foo : public Foo{
public:
    MOCK_CONST_METHOD0(value, int());
    MOCK_METHOD1(setValue, void(const int));
};

Foo_Test.h

#include "gtest/gtest.h" 
#include "Mock_Foo.h"
TEST(FooTest, foo){
  Mock_Foo foo;
  Bar bar{&foo};

  EXPECT_CALL(foo, value());

  bar.doStuff();
}

[Corey Kosak]

It would be straightforward to introduce a new set of macros to support this. These new macros might look like

MOCK_NOEXCEPT_METHOD_{0 through 10}

MOCK_CONST_NOEXCEPT_METHOD_{0 through 10}

I'm not sure whether the GMock team wants to do this. They may be concerned about the doubling (and in the future, exponential growth) of the number of macros gMock defines. If you wanted to do this "for now" in your own copy of gMock I could show you how to get started.

If you're stuck and want a workaround, you could do something like this

changes to Mock_Foo.h:

    virtual int value() const noexcept{ return value_hack(); }  // forward all calls to value_hack

    MOCK_CONST_METHOD0(value_hack, int());  // mock value_hack instead of mocking value

changes to "Foo_Test.h" (I think you meant Foo_Test.cc):

  EXPECT_CALL(foo, value_hack());   // set expectations on value_hack instead of value

The above isn't pretty, and it's probably officially frowned upon, but at the very least it will get you unstuck.

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[Edgar]

On Friday, July 24, 2015 at 1:58:48 PM UTC-3, Alex Shaver wrote:

If a function has 'noexcept' keyword, I don't know if I can mock it. The initial compiling (gcc or clang) complains:

Mock_Foo.h:10:24: error: exception specification of overriding function is more lax than base version

MOCK_CONST_METHOD0(value, int());

                   ^

/gmock-svn/include/gmock/gmock-generated-function-mockers.h:687:62: note: expanded from macro 'MOCK_CONST_METHOD0'

#define MOCK_CONST_METHOD0(m, ...) GMOCK_METHOD0_(, const, , m, __VA_ARGS__)

                                                             ^

/gmock-svn/include/gmock/gmock-generated-function-mockers.h:357:37: note: expanded from macro 'GMOCK_METHOD0_'

GMOCK_RESULT_(tn, __VA_ARGS__) ct Method( \

                                  ^

Foo.h:10:17: note: overridden virtual function is here

virtual int value() const noexcept{ return _value; }

            ^

Here's the sample code used to generate:

Foo.h:

class Foo{
public:
  Foo();
  ~Foo();


  virtual int value() const noexcept{ return _value; }
  virtual void setValue(const int value){ _value = value; }


private:
  int _value;
};

 

Hi Alex:

I submitted a patch a while back which would allow:

  MOCK_QUALIFIED_METHOD0(value, const noexcept, int());

https://codereview.appspot.com/103030043/
See the test for a full example.

- Edgar

[Alex Shaver]

Oh that's cool. If it gets into the main branch I'll have to take a look at it.