Bug #3368
closed
Code style rule 3.11 is wrong
100%
Description
Rule 3.11 states the following:
When checking if shared_ptr points to an object, explicit static_cast<bool> must be used.
shared_ptr in C++11 (unlike boost::shared_ptr) does not have implicit conversion to bool.
This is simply wrong. The fact that operator bool() is declared explicit in std::shared_ptr does NOT matter in a boolean context. This is true practically every time a shared_ptr is checked for validity.
The idiomatic way is:
shared_ptr<T> ptr;
if (ptr) { ... }
// OR
if (ptr == nullptr) { ... }
// OR
if (ptr != nullptr) { ... }
// etc...
Moreover, if the implicit conversion isn't possible (when not in a boolean context), the compilation will fail, so there's really no reason why this has to be a code style rule.
Updated by Alex Afanasyev almost 9 years ago
I agree. I wrote this rule based on my misunderstanding of implicit conversion and compilation errors I was getting. Unfortunately, I don't remember a specific case of that error.
@Davide, do mind updating it? We could simply remove the rule (but keep the number reserved).
Updated by Davide Pesavento almost 9 years ago
- Assignee changed from Junxiao Shi to Davide Pesavento
- Start date deleted (
12/22/2015)
Sure.
An example where you get an error is a function return, in that case you need an explicit cast or it won't compile. But even in that case I'd prefer using == nullptr or != nullptr rather than the cast.
bool
foo()
{
auto ptr = make_shared<T>(...);
//return ptr; // FAIL
//return static_cast<bool>(ptr); // OK, but ugly
return (ptr != nullptr); // OK, better
}
Updated by Davide Pesavento almost 9 years ago
- Subject changed from Rule 3.11 is wrong to Code style rule 3.11 is wrong
- Status changed from New to Code review
- Priority changed from Normal to Low
- Target version set to v0.4
- % Done changed from 0 to 100
Updated by Junxiao Shi almost 9 years ago
- Project changed from NFD to ndn-cxx
- Category changed from Docs to Docs
- Target version changed from v0.4 to v0.4
Updated by Alex Afanasyev almost 9 years ago
- Status changed from Code review to Closed