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[doc,committed] Re: Doc question: is "templatized" a word?

Message ID 58A68132.5060106@codesourcery.com
State New
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Sandra Loosemore Feb. 17, 2017, 4:50 a.m. UTC 
On 02/15/2017 01:17 PM, Jason Merrill wrote:
> On Wed, Feb 15, 2017 at 1:57 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> On 15 February 2017 at 15:53, Jason Merrill wrote:
>>> On Sat, Feb 11, 2017 at 4:19 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>>>> On 11 February 2017 at 20:36, Sandra Loosemore wrote:
>>>>> On 02/11/2017 06:21 AM, Jonathan Wakely wrote:
>>>>>>
>>>>>> On 11 February 2017 at 08:48, Gerald Pfeifer wrote:
>>>>>>>
>>>>>>> On Fri, 10 Feb 2017, Sandra Loosemore wrote:
>>>>>>>>
>>>>>>>> The documentation for -Wno-non-template-friend refers to
>>>>>>>> "non-templatized
>>>>>>>> friend functions" and "templatized functions".  I don't see the term
>>>>>>>> "templatized" used anywhere in the C++ standard.  This paragraph also
>>>>>>>> uses
>>>>>>>> "nontemplate function", which I assume refers to the same thing the C++
>>>>>>>> standard spells "non-template function".  So does "non-templatized
>>>>>>>> function"
>>>>>>>> also mean "non-template function"?  Or does it have some other meaning?
>>>>>>>
>>>>>>>
>>>>>>> I would avoid "templatized" and believe "non-template function" is
>>>>>>> more appropriate in your example.
>>>>>>
>>>>>>
>>>>>> Yes,
>>>>>>
>>>>>> s/non-templatized/non-template/
>>>>>> s/nontemplate/non-template/
>>>>>> s/templatized function/function template/
>>>>>>
>>>>>> But I wonder if that warning is even useful nowadays. The example of
>>>>>> "friend foo(int);" is bogus and is correctly rejected:
>>>>>>
>>>>>> fr.cc:2:17: error: ISO C++ forbids declaration of ‘foo’ with no type
>>>>>> [-fpermissive]
>>>>>>      friend foo(int);
>>>>>>                    ^
>>>>>
>>>>>
>>>>> I hadn't actually gotten that far :-) but it looks like that's an
>>>>> implicit-int error unrelated to the actual purpose of this option.
>>>>>
>>>>> This ended up on my todo list firstly because "templatized" didn't
>>>>> spell-check, and secondly because the "new compiler behavior" documented in
>>>>> connection with this option has existed at least since 1998 and can hardly
>>>>> be considered "new" any more.  Also I think the reference to section 14.5.3
>>>>> of the C++ standard is bit-rotten (it's 14.5.4 in the c++0x draft I have
>>>>> handy).
>>>>>
>>>>> I'll leave it up to the C++ experts to decide whether the option should just
>>>>> be removed and the warning replaced with a hard error controlled by some
>>>>> other flag.
>>>>
>>>> It definitely shouldn't be turned into a hard error, the warning
>>>> complains about valid code, such as:
>>>>
>>>> template<typename T> struct A {
>>>>    friend int foo(T);
>>>> };
>>>>
>>>> int main() {
>>>>    A<int> a;
>>>> }
>>>>
>>>> I think it warns because the meaning of that code changed, a *long*
>>>> time ago, so it's saying "if you wrote this code in the 1990s it might
>>>> do something different to what you expect."
>>>>
>>>> I'm not sure how useful that warning is now, although EDG warns for it
>>>> too (with a fix-it hint that I think is bogus):
>>>>
>>>> "fr.cc", line 2: warning: "int foo(T)" declares a non-template function -- add
>>>>            <> to refer to a template instance
>>>>      friend int foo(T);
>>>>                 ^
>>>
>>> That fix-it looks fine to me;
>>
>> Where should I add the <> to make it valid?
>>
>> If I change the example to "friend int foo<>(T);" EDG says it's not a template:
>>
>> template<typename T> struct A {
>>    friend int foo<>(T);
>> };
>>
>> int main() {
>>    A<int> a;
>> }
>>
>> "fr.cc", line 2: error: foo is not a template
>>      friend int foo<>(T);
>
> Yep, you would also need to declare the foo template earlier in the TU.
>
> Jason
>

Thanks everyone for the explanations and suggestions.  I've checked in 
the attached patch to clean this up.

-Sandra
diff mbox

Patch

Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi	(revision 245524)
+++ gcc/doc/invoke.texi	(working copy)
@@ -2996,19 +2996,13 @@  But this use is not portable across diff
 @item -Wno-non-template-friend @r{(C++ and Objective-C++ only)}
 @opindex Wno-non-template-friend
 @opindex Wnon-template-friend
-Disable warnings when non-templatized friend functions are declared
-within a template.  Since the advent of explicit template specification
-support in G++, if the name of the friend is an unqualified-id (i.e.,
-@samp{friend foo(int)}), the C++ language specification demands that the
-friend declare or define an ordinary, nontemplate function.  (Section
-14.5.3).  Before G++ implemented explicit specification, unqualified-ids
-could be interpreted as a particular specialization of a templatized
-function.  Because this non-conforming behavior is no longer the default
-behavior for G++, @option{-Wnon-template-friend} allows the compiler to
-check existing code for potential trouble spots and is on by default.
-This new compiler behavior can be turned off with
-@option{-Wno-non-template-friend}, which keeps the conformant compiler code
-but disables the helpful warning.
+Disable warnings when non-template friend functions are declared
+within a template.  In very old versions of GCC that predate implementation
+of the ISO standard, declarations such as 
+@samp{friend int foo(int)}, where the name of the friend is an unqualified-id,
+could be interpreted as a particular specialization of a template
+function; the warning exists to diagnose compatibility problems, 
+and is enabled by default.
 
 @item -Wold-style-cast @r{(C++ and Objective-C++ only)}
 @opindex Wold-style-cast