non-type parameter template problem

[jjw358]

i have a .h file that includes the following
template<std::size_t n>
class simplesusp {
public:
simplesusp();

};

in my .cc file, i try to say
simplesusp<8> s;

and i get the following msg from g++
undefined reference to `simplesusp<8u>::simplesusp()'

not sure what i'm doing wrong, any help would be appreciated

 

[spongejon]

i have a .h file that includes the following
template<std::size_t n>
class simplesusp {
 public:
  simplesusp();

};

in my .cc file, i try to say
simplesusp<8> s;

and i get the following msg from g++
undefined reference to `simplesusp<8u>::simplesusp()'

not sure what i'm doing wrong, any help would be appreciated

you haven't implemented
simplesusp<8u>::simplesup()

try

template<std::size_t n>
class simplesusp {
public:
simplesusp(){}
};

 

[jjw358]

sorry let me clarify:
in simplesusp.h i have
template<std::size_t n>
class simplesusp {
public:
simplesusp(){}
};

in simplesusp.cc i have

template<std::size_t n>
simplesusp<n>::simplesusp() { //something stuff }

in main.cc i have
simplesusp<8> s;

g++ gives me:
undefined reference to `simplesusp<8u>::simplesusp()'

help again appreciated. thx

 

[jjw358]

sorry let me clarify,

in simplesusp.h, i have
template<std::size_t n>
class simplesusp {
public:
simplesusp();

};

in simplesusp.cc, i have
template<std::size_t n>
simplesusp<n>::simplesusp() { // some stuff }

in main.cc, i have
simplesusp<8> s;

and i get the following msg from g++
undefined reference to `simplesusp<8u>::simplesusp()'

not sure what i'm doing wrong, any help would be appreciated

 

[Noah Roberts]

sorry let me clarify,

in simplesusp.h, i have
template<std::size_t n>
class simplesusp {
public:
simplesusp();

};

in simplesusp.cc, i have
template<std::size_t n>
simplesusp<n>::simplesusp() { // some stuff }

in main.cc, i have
simplesusp<8> s;

and i get the following msg from g++
undefined reference to `simplesusp<8u>::simplesusp()'

not sure what i'm doing wrong, any help would be appreciated

extern templates are not yet part of the standard. You therefore cannot
put template definitions in a cpp file and expect the compiler to know
you want other cpp files to have access to them. You need to put them
in headers.

http://www.parashift.com/c++-faq-lite/templates.html#faq-35.14

 

[Ian Collins]

extern templates are not yet part of the standard.

They are (export), but hardly anyone implements them.

You therefore cannot
put template definitions in a cpp file and expect the compiler to know
you want other cpp files to have access to them. You need to put them
in headers.

You can with some compilers which don't implement export but do have
their own rules for locating template definitions.

 

[spongejon]

Out of interest....

You mean "simplesusp();", right? Because otherwise you would be
violating the one definition rule.

Which part of the one definition rule is violated by using simplesusp()
{} ?