Hi all,

I'm a bit confused why the code below actually compiled (msvc 8.0):

=====================BEGIN CODE======================
#include <iostream>

template<bool test>
struct a_templated_struct { a_templated_struct() { std::cout <<
global_var << std::endl; } };

int _tmain(int argc, _TCHAR* argv[])
{
a_templated_struct<true> var;
return 0;
}

const char* global_var = "a global var";

=====================END CODE======================

Isn't the spec (Bjarne Stroustrup) saying that the scope of a global
name starts from the point of declaration until the end of the
translation unit (4.9.4) And this rule also applies to undependable
names in template definitions (C.13.8.2). And then there is C.13.8.3
and C.13.8.4. But still, it seems to me that global_var shouldn't be
visible to anyone. Could someone explain me the rule playing here?
Much appreciated.

Pieter.

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Hi

podb.visys@gmail.com wrote:

> Hi all,
>
> I'm a bit confused why the code below actually compiled (msvc 8.0):
>
> =====================BEGIN CODE======================
> #include <iostream>
>
> template<bool test>
> struct a_templated_struct { a_templated_struct() { std::cout <<
> global_var << std::endl; } };
>
> int _tmain(int argc, _TCHAR* argv[])
> {
> a_templated_struct<true> var;
> return 0;
> }
>
> const char* global_var = "a global var";
>
> =====================END CODE======================

GCC 4.3.0 doesn't compile it. And, like you, I think it shouldn't compile.
The error message is as expected:

t.cc: In constructor 'a_templated_struct<test>::a_templated_struct()':
t.cc:7: error: 'global_var' was not declared in this scope

Markus


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podb.visys@gmail.com wrote:
> Hi all,
>
> I'm a bit confused why the code below actually compiled (msvc
> 8.0):
>
> =====================BEGIN CODE======================
> #include <iostream>
>
> template<bool test>
> struct a_templated_struct { a_templated_struct() { std::cout <<
> global_var << std::endl; } };
>
> int _tmain(int argc, _TCHAR* argv[])
> {
> a_templated_struct<true> var;
> return 0;
> }
>
> const char* global_var = "a global var";
>
> =====================END CODE======================
>
> Isn't the spec (Bjarne Stroustrup) saying that the scope of a global
> name starts from the point of declaration until the end of the
> translation unit (4.9.4) And this rule also applies to undependable
> names in template definitions (C.13.8.2). And then there is C.13.8.3
> and C.13.8.4. But still, it seems to me that global_var shouldn't be
> visible to anyone. Could someone explain me the rule playing here?
> Much appreciated.
>

The problem here is that the compiler doesn't implement the 2 phase
lookup properly.

It should detect that global_var is not visible at the point of
definition of the template, and not just use some name that happens to
appear later. Other compilers catch this.


Bo Persson







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