Re: Template name lookup
jacob navia wrote:
Victor Bazarov wrote:
jacob navia wrote:
Suppose a template like this:
template <typename T> class Index : public DataNode<T>
{
// Many lines of code later
static void Insert(UpdateBlock* ub)
{
if (GlobalVar) {
}
}
}
Many lines later
extern int GlobalVar;
No instantiations of the template are done before the declaration
of "GlobalVar"
This code is compiling with
o gcc
o msvc
o solaris sparc sun compiler
o IBM AIX xlc version 8.
BUT
With version 9 of the IBM compiler this doesn't work any more since
the compiler tell us that "GlobalVar" is not declared at template
definition time.
Who is correct?
All other compilers or IBM xlc version 9?
The 'GlobarVar' is supposed to be visible at the point of first use
(in the template definition), see [temp.res]/9.
Thanks for your quick answer. Maybe can you explain what
[temp.res]/9 means? (I am new here)
It is a reference to a paragraph in the Standard. [temp.res] is the
subclause, 9 is the paragraph number. If you need to look it up,
open the Standard, find "[temp.res]", scroll down to the 9th para.
That means that gcc, msvc, solaris, xlc v8, are all wrong if they
accept the code as is.
Well... thanks but this is just incredible.
Not really. Name lookup rules are sometimes quite strict and the
compiler vendors feel like they are doing us a favour if they let
us write code like that. You might want to try your compilers
with this:
template<class T> struct B {};
template<class T> struct A : B<T>
{
static int foo() { return GlobalVar; } // line 4
};
extern int GlobalVar;
int main() {
return A<char>::foo();
}
If they compile this, they are in violation of the rule set forth
in Standard, [temp.res]/9. I tried it with Comeau online, it did
not compile it ('GlobalVar' is undefined on line 4). VC++ 2005
compiled it. VC++ 2008 EE compiled it.
V
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