This PR affirms that all virtual functions, *including destructors*,
should be declared exactly one of `virtual`, `override`, or `final`, and
takesa pass through the document to make the examples and guidance
consistent with that.
Of course a virtual destructor is a virtual function: It behaves
polymorphically, and it has a vtable entry that can be overwritten ==
overridden in a derived class exactly the same as any other derived
virtual override. See also [class.virtual]/7: "Even though destructors
are not inherited, a destructor in a derived class overrides a base
class destructor declared virtual; see [class.dtor] and [class.free]."
However, the following exception text currently appears in C.128:
> If a base class destructor is declared `virtual`, one should avoid
declaring derived class destructors `virtual` or `override`. Some code
base and tools might insist on `override` for destructors, but that is
not the recommendation of these guidelines.
... but this exception is (a) not well-founded, and (b) inconsistent
with the Guidelines' practice in other examples and with the rationale a
few lines earlier for C.128 itself.
Re (a):
- The exception is overly broad: The rationale given for this exception
is entirely against marking destructors `override` (not `virtual`). So
clearly the exception to write neither keyword is too broad: At most,
the exception should be to write `virtual` rather than `override`.
- Explicit `virtual` is primarily for class users, not class authors:
The arguments given in #721 favoring this exception are from the
viewpoint of the implementation of the function (even then, the
arguments are debatable and debated). But `virtual`, `override`, and
`final` are primarily for the far larger audience of *class users and
call sites* of the function, for whom of course we should document each
declared function that is polymorphic, *especially* the destructor --
this tells calling code whether the function is safe to call through a
(smart or built-in) pointer or reference to base, which will nearly
always be the case for such types. We should not make the reader of the
code go way to look in the base classes to figure out whether a function
declared in this class is virtual or not -- the reason this Item exists
is primarily to avoid that implicit virtual antipattern via convention
and automated enforcement. For class users, all virtual functions
including destructors are equally polymorphic.
Re (b): The Guidelines already don't follow this. For instance, two
Items later (in C.130) we have this example that correctly uses
`override`:
~~~
virtual ~D() override;
~~~
... though per C.128 it should not also specify `virtual` (also fixed in
this PR).
Finally, the exception also contradicts the rationale given earlier in
the same Item.
- "a C-style, zero-terminated strings" is wrong, it must be either "C-style, zero-terminated strings" or "a C-style, zero-terminated string"
- added hint to `std::string_view
* Add example code for T.48
* Fix whitespace in end of line
* Use better syntax for concept constraint
* Revert "Use better syntax for concept constraint"
This reverts commit f071920d7f.
* reword the A.1 rule title
* add candidate content for the A.1 rule
* make minor improvements to the A.2 note
* simplify wording in the first bullet of A.4's Reason
* Tighten up CP.1
* balanced verb usage in first sentence
* changed third sentence to "libraries not using threads", as I
believe this was the original author's intended meaning.
* clarified "this" in fourth sentence
* cut wordiness of "thanks to the magic of cut-and-paste", as it
added no value
* changed "Example" heading to "Example, bad"
* added "bad:" comment above statics in the example
* added an explanatory sentence immediately after the example
* changed "works perfectly in a single-threaded" after example to
"works as intended in a single threaded". Also balanced the
structure of the two comma separated phrases inside this sentence.
* strengthened parenthetical explanation in second bullet of "could
be made safe" section
* Correct grammar mistake pointed out by @cubbimew
* Remove specific cache details in CP.1 per @hsutter's request
* Added bad and goof example to NR.5 in CppCoreGuidelines.md
Added bad and good example to NR.5 Don’t: Don’t do substantive work in a constructor; instead use two-phase initialization.
I think it could be suitable.
* adjusted coding style
* removed extra space
* removed one more whitespace
* removed spaces before note to make it a blank line
* made Cleanup method from bad example return void
* some changes after review comments
- removed try catch
- removed defaulted dtor
- changed int to size_t, removed check for even.
- Expects() for invariant check
- typo
* spell check adjustment
* moved comment up for met the line length
* changed variablename in good example
... they were named same after removed the try catch scope
* changed afer comments
- changed check_size() function to a static member function
- fixed comment mentioning the default contract violation behavior.
* C.129 Fix typos and conjugation
I noticed some grammatical errors in this section and fixed them to match my interpretation of the author's intention.
* One more fix
Pluralization
* Use `memoizes` instead of `mnemonizes` in the context of caching
While apparently, 'mnemonizes' is a word, I don't think it's the best choice here.
* Update isocpp.dic
hsutter
beinhaerter
alexcamposruiz
jkorinth
Louis Cloete
Sergey Zubkov
Dave Smith
Florian Thake
Kyle
Aleksander
Paul Romano
Taewon Park
Saad
Amir Livneh