g++: change in behaviour since gcc-2.95.2

g++: change in behaviour since gcc-2.95.2

[Martin Reinecke]

Consider the following code snippet:

class MSG_STREAM
  {
  public:
    template<typename T> MSG_STREAM &operator<< (const T &data) {}
  };

MSG_STREAM *simple_manip (MSG_STREAM &blah) {}

int main()
  {
  MSG_STREAM foo;
  foo << 5 << simple_manip;
  }

gcc 2.95.2 compiles this without complaints, while the current CVS version says

test.cc: In function `int main ()':
test.cc:12: no match for `MSG_STREAM & << MSG_STREAM *(&) (MSG_STREAM &)'

Is this new behaviour according to the standard? If so, could you please point
me to some information why pointers to functions cannot be used as template
parameter types?

Thanks in advance,
  Martin

Re: g++: change in behaviour since gcc-2.95.2

[Martin v. Loewis]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 622 bytes --]

> Is this new behaviour according to the standard? If so, could you
> please point me to some information why pointers to functions cannot
> be used as template parameter types?

I'm not entirely sure, but I believe this is due to 14.8.2/2

# Type deduction may fail for the following reasons:
# ...
#  - Attempting to create a cv­qualified function type.

Of course, this is not exactly the right place, since we have no
explicit template arguments, but deduction. The apparent intent is
that it applies to the deduced arguments as well, since there are no
cv-qualified function types in C++.

Hope this helps,
Martin

Re: g++: change in behaviour since gcc-2.95.2

[Martin v. Loewis]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 622 bytes --]

> Is this new behaviour according to the standard? If so, could you
> please point me to some information why pointers to functions cannot
> be used as template parameter types?

I'm not entirely sure, but I believe this is due to 14.8.2/2

# Type deduction may fail for the following reasons:
# ...
#  - Attempting to create a cv­qualified function type.

Of course, this is not exactly the right place, since we have no
explicit template arguments, but deduction. The apparent intent is
that it applies to the deduced arguments as well, since there are no
cv-qualified function types in C++.

Hope this helps,
Martin

g++: change in behaviour since gcc-2.95.2

[Martin Reinecke]

Consider the following code snippet:

class MSG_STREAM
  {
  public:
    template<typename T> MSG_STREAM &operator<< (const T &data) {}
  };

MSG_STREAM *simple_manip (MSG_STREAM &blah) {}

int main()
  {
  MSG_STREAM foo;
  foo << 5 << simple_manip;
  }

gcc 2.95.2 compiles this without complaints, while the current CVS version says

test.cc: In function `int main ()':
test.cc:12: no match for `MSG_STREAM & << MSG_STREAM *(&) (MSG_STREAM &)'

Is this new behaviour according to the standard? If so, could you please point
me to some information why pointers to functions cannot be used as template
parameter types?

Thanks in advance,
  Martin