fails to link with GCC on mac .. works with VC on Win. What's wrong and how to fix?

[Inertial]

"Jonathan Lee" wrote in message

I haven't checked the spec, but this appears to be working as
a declaration instead of definition. I did the following and it
worked fine...

template<>
class Test<int> {
public:
class SubClass {

public:
SubClass() : i(1) {}
int i;
};
static SubClass statics;
};

Test<int>::SubClass Test<int>::statics;

That gets an error in more recent standard conforming gcc complers .. you
get

error: too few template-parameter-lists

Also, this worked, but implies a copy constructor

template<> Test<int>::SubClass Test<int>::statics = SubClass();

That *may* help me though .. but still would be nice to avoid that

I haven't checked, but I assume the way you wrote it is
being treated as specialization only, and not definition.

That is what I am thinking . .but don't see yet why that is or how to force
it to be a definition.

 

[Öö Tiib]

"Öö Tiib"  wrote in message








What DEVC++ project file? Just freshly installed a GCC environment .. used
"c++ bug.cpp" where bug.cpp is the 'bad' code, and get the error.  Also used
the gcc compiler for XCode on a Mac .. same thing.  VS2008 C++ compiler
doesn't complain, however, but its not as standard conforming.

Have YOU tried to compile the examples that failed (and worked) that I
posted .. and if so, using which compiler and version?

I tried with icc 10 and VS 2005. Comeau online does not link and no
gcc on this PC. Did you actually try to remove that template<> there?
It is strange that your compiler requires it.

 

[Jonathan Lee]

"Jonathan Lee"  wrote in message



That gets an error in more recent standard conforming gcc complers .. you
get

error: too few template-parameter-lists

Really? Doesn't do it for me on g++ 4.4.4 and that's pretty new...

--Jonathan

 

[Inertial]

"Ian Collins" wrote in message news:[email protected]...

That is how it should be.

No .. it shouldn't .. that gives error ...

error: too few template-parameter-lists

see http://c2.com/cgi/wiki?TooFewTemplateParameterLists

"Too Few Template-Parameter-Lists is an error message produced by newer
versions of the GnuCpp compiler for code which previously compiled. The
problem concerns the initialization of static members of a templated class.
Previously it was sufficient to declare the member, but this now has to be
preceded by template <>."

 

[Inertial]

"Jonathan Lee" wrote in message

Really? Doesn't do it for me on g++ 4.4.4 and that's pretty new...

I've got 4.3 here on windows .. where do I get a build 4.4.4 for Windows?
Also using it on XCode on Mac which is 4.2

Also refer to

http://c2.com/cgi/wiki?TooFewTemplateParameterLists

"TooFewTemplateParameterLists is an error message produced by newer versions
of the GnuCpp compiler for code which previously compiled. The problem
concerns the initialization of static members of a templated class.
Previously it was sufficient to declare the member, but this now has to be
preceded by template <>."

Has this changed since 4.3 ??

 

[Jonathan Lee]

"Ian Collins"  wrote in message


No .. it shouldn't .. that gives error ...

error: too few template-parameter-lists

seehttp://c2.com/cgi/wiki?TooFewTemplateParameterLists

"Too Few Template-Parameter-Lists is an error message produced by newer
versions of the GnuCpp compiler for code which previously compiled. The
problem concerns the initialization of static members of a templated class.
Previously it was sufficient to declare the member, but this now has to be
preceded by template <>."

I think you're missing the specialization of Test that I added.

--Jonathan

 

[Inertial]

"Jonathan Lee" wrote in message

I think you're missing the specialization of Test that I added.

I tried your code

==
template<>
class Test<int> {
public:
class SubClass {

public:
SubClass() : i(1) {}
int i;
};
static SubClass statics;
};

Test<int>::SubClass Test<int>::statics;

int main(int argc, char* const argv[])
{
int j = statics.i;
return 0;
}
==

and get

bug5.cpp:2: error: 'Test' is not a template
bug5.cpp:2: error: explicit specialization of non-template 'Test'
bug5.cpp:13: error: 'Test' is not a template
bug5.cpp:13: error: expected initializer before 'Test'
bug5.cpp: In function 'int main(int, char* const*)':
bug5.cpp:17: error: 'statics' was not declared in this scope
--Jonathan

 

[Jonathan Lee]

"Jonathan Lee"  wrote in message

I think you're missing the specialization of Test that I added.

I tried your code
[snip]

and get

bug5.cpp:2: error: 'Test' is not a template
bug5.cpp:2: error: explicit specialization of non-template 'Test'
bug5.cpp:13: error: 'Test' is not a template
bug5.cpp:13: error: expected initializer before 'Test'
bug5.cpp: In function 'int main(int, char* const*)':
bug5.cpp:17: error: 'statics' was not declared in this scope
--Jonathan

Sorry, I assumed you would keep the original class template.
For the sake of completeness:

template <class T>
class Test {
public:
class SubClass {

public:
SubClass() : i(1) {}
int i;
};
static SubClass statics;
};

template<>
class Test<int> {
public:
class SubClass {

public:
SubClass() : i(1) {}
int i;
};
static SubClass statics;
};

Test<int>::SubClass Test<int>::statics;

int main(int argc, char* argv[])
{
int j = Test<int> :: statics.i;
return 0;
}

--Jonathan

 

[Öö Tiib]

"Jonathan Lee"  wrote in message



I've got 4.3 here on windows .. where do I get a build 4.4.4 for Windows?
Also using it on XCode on Mac which is 4.2

Also refer to

http://c2.com/cgi/wiki?TooFewTemplateParameterLists

"TooFewTemplateParameterLists is an error message produced by newer versions
of the GnuCpp compiler for code which previously compiled. The problem
concerns the initialization of static members of a templated class.
Previously it was sufficient to declare the member, but this now has to be
preceded by template <>."

Has this changed since 4.3 ??

What happens if you do not specialize that Test<int>::statics? I mean
write something like:

template<class T> typename Test<T> :: SubClass Test<T> :: statics;

 

[Inertial]

"Jonathan Lee" wrote in message

Sorry, I assumed you would keep the original class template.
For the sake of completeness:

]snip]

EWW .. having to specify the whole class twice seems a bit on the awful side

This works just fine, however

===
template <class T> class Test {
public:
class SubClass {
public:
SubClass() : i(1) {}
int i;
};
static SubClass statics;
};

template<> Test<int> :: SubClass Test<int> :: statics = Test<int> ::
SubClass();

int main(int argc, char* const argv[])
{
int j = Test<int> :: statics.i;
return 0;
}
===

No copy constructor or operator = required .. so hoping it also doesn't
double construct.

 

[Jonathan Lee]

Yes, it looks like the declaration of a specialisation.

Just for anyone who is wondering, I dug up the relevant part of
the spec (emphasis mine):

[temp.expl.spec]

14. An explicit specialization of a static data
member of a template is a definition if the declaration includes
an initializer; otherwise, it is a *declaration*. [Note: there is
*no* syntax for the definition of a static data member of a
template that requires default initialization.

template<> X Q<int>::x;

15. This is a *declaration* regardless of whether X can be
default initialized. -- end note]

--Jonathan

 

[Inertial]

"Jonathan Lee" wrote in message

Yes, it looks like the declaration of a specialisation.

Just for anyone who is wondering, I dug up the relevant part of
the spec (emphasis mine):

[temp.expl.spec]

14. An explicit specialization of a static data
member of a template is a definition if the declaration includes
an initializer; otherwise, it is a *declaration*. [Note: there is
*no* syntax for the definition of a static data member of a
template that requires default initialization.
Nasty

template<> X Q<int>::x;

But this form will work (in my case at least) ...

15. This is a *declaration* regardless of whether X can be
default initialized. -- end note]

 

[Inertial]

"Inertial" wrote in message

DAMNIT !!!

All is fine .. except in my REAL example, one of my members explicitly has a
private copy constructor .. so it is the equivalent of this ...

==
class NoCopyConstructor {
public:
NoCopyConstructor() {}
private:
NoCopyConstructor(const NoCopyConstructor& x); // no copy constructor
};

template <class T> class Test {
public:
class InnerClass {
public:
InnerClass() : i(1) {}
int i;
NoCopyConstructor x;
};
static InnerClass statics;
};

template<> Test<int> :: InnerClass Test<int> :: statics = Test<int> ::
InnerClass();

int main(int argc, char* const argv[])
{
int j = Test<int> :: statics.i;
return 0;
}
==

And THAT fails to compile. So think I might put in a dummy arg to the
constructor for the InnerClass and see if that works .. let you know :

 

[Inertial]

"Inertial" wrote in message

ok .. now THIS works ok

==
class NoCopyConstructor {
public:
NoCopyConstructor() {}
private:
NoCopyConstructor(const NoCopyConstructor& x); // no copy constructor
};

template <class T> class Test {
public:
class InnerClass {
public:
InnerClass(bool) : i(1) {}
T i;
NoCopyConstructor x;
};
static InnerClass statics;
};

template<> Test<int> :: InnerClass Test<int> :: statics(true);

int main(int argc, char* const argv[])
{
int j = Test<int> :: statics.i;
return 0;
}
==

 

[Öö Tiib]

"Inertial"  wrote in message




DAMNIT !!!

All is fine .. except in my REAL example, one of my members explicitly has a
private copy constructor .. so it is the equivalent of this ...

==
class NoCopyConstructor {
public:
    NoCopyConstructor() {}
private:
    NoCopyConstructor(const NoCopyConstructor& x);    // no copy constructor

};

template <class T> class Test {
public:
    class InnerClass {
    public:
        InnerClass() : i(1) {}
        int i;
        NoCopyConstructor x;
    };
    static InnerClass statics;

};

template<> Test<int> :: InnerClass Test<int> :: statics = Test<int> ::
InnerClass();

int main(int argc, char* const argv[])
{
    int j = Test<int> :: statics.i;
    return 0;}

==

And THAT fails to compile.  So think I might put in a dummy arg to the
constructor for the InnerClass and see if that works .. let you know :

Still why you do not try it without that specialization?

template<class T> typename Test<T> :: InnerClass Test<T> :: statics;

 

[Inertial]

"Öö Tiib" wrote in message

Still why you do not try it without that specialization?

template<class T> typename Test<T> :: InnerClass Test<T> :: statics;

That seems to work too

But in my real project ding it that way won't help, as that doesn't actually
force the definition of statics at a particular point in code .. and for
order of construction/destruction I have to make it define given instances
of the class at a particular point in a particular file.

Thanks tho

 

[Ian Collins]

"Öö Tiib" wrote in message


That seems to work too

But in my real project ding it that way won't help, as that doesn't
actually force the definition of statics at a particular point in code
.. and for order of construction/destruction I have to make it define
given instances of the class at a particular point in a particular file.

That is never a good idea! It'll work fine until something gets added,
or something gets moved to another file.

 

[gwowen]

"Jonathan Lee"  wrote in message
I've got 4.3 here on windows .. where do I get a build 4.4.4 for Windows?
Also using it on XCode on Mac which is 4.2

If you're using the Mingw compiler on Windows, you can get gcc 4.4 and
4.5 from
http://tdm-gcc.tdragon.net/

 

[Vladimir Jovic]

What happens if you do not specialize that Test<int>::statics? I mean
write something like:

template<class T> typename Test<T> :: SubClass Test<T> :: statics;

I tried that on g++ 4.3, and it compiled fine.



If it helps, next code also compiles fine :

template <class T> class Test {
public:
class SubClass {
public:
SubClass() : i(1) {}
int i;
};
static SubClass& statics(){
static SubClass localStatics;
return localStatics;
}
};


int main(int argc, char* argv[])
{
int j = Test<int>::statics().i;
return 0;
}