Hi That sounds great.
Can we also do the same for const RetainPtr ? Thanks > On 13 Nov 2024, at 4:49 PM, Ryosuke Niwa via webkit-dev > <webkit-dev@lists.webkit.org> wrote: > > Instead of introducing a new smart pointer type like SetOnceRefPtr, we’re > going to use `const RefPtr`, `const Ref`, `const unique_ptr`, and `const > UniqueRef`. `const Ref` and `const UniqueRef` are used for values that are > initialized in the constructor and never changed. `const RefPtr` and `const > unique_ptr` are used for lazily initialized values. We introduce a > `initializeOnce(ptr, v)` function which takes `const RefPtr` or `const > unique_ptr` ptr and sets it to v. The static analyzer will be updated to > recognize this pattern. > > https://bugs.webkit.org/show_bug.cgi?id=283038 > https://github.com/llvm/llvm-project/pull/115594 > > - R. Niwa > >> On Oct 29, 2024, at 2:49 AM, youenn fablet <youe...@gmail.com> wrote: >> >> FWIW, there are many classes with Ref<> members that are initialized in the >> constructor and are never intended to be changed. >> I was hoping we would cover this case at least. The RefPtr lazy >> initialization is a welcome addition as well. >> >> I think this would be useful to improve readability: >> - Too many protected in the same line of code makes code harder to read for >> me. >> - It is easier to reason about "stable" member variables. Having an explicit >> type or some annotation instead of having to look at the whole code is an >> improvement. >> >> Le mar. 29 oct. 2024 à 03:10, Jean-Yves Avenard via webkit-dev >> <webkit-dev@lists.webkit.org> a écrit : >>> Hi >>> >>> It’s a very strong +1 for me ; I find the usage of >>> foo->protectedBar()->method() or Ref { foo->bar() }->method() >>> particularly unsightly (and points more to the inability of the static >>> analyser to deal with some use case than the code being inherently unsafe) >>> >>> Having a way to reduce the unsightly pattern where we are 100% certain it’s >>> not needed is a benefit. >>> I assume also that the static analyser will not complain with `const` >>> members either >>> >>> (For the sake of disclosure, I asked Ryosuke for that feature after >>> discussing the need with Youenn) >>> >>> Jean-Yves >>> >>>> On 29 Oct 2024, at 5:48 am, Ryosuke Niwa via webkit-dev >>>> <webkit-dev@lists.webkit.org> wrote: >>>> >>>> Hi all, >>>> >>>> In WebKit, it’s fairly common to write a member variable as RefPtr or >>>> std::unique_ptr that later gets lazily initialized to some value but never >>>> unset or assigned of a different value after that. >>>> >>>> e.g. >>>> >>>> class Foo { >>>> Bar& bar() { >>>> if (!m_bar) >>>> m_bar = Bar::create(); >>>> return *m_bar; >>>> } >>>> Ref<Bar> protectedBar() { return bar(); } >>>> >>>> RefPtr<Bar> m_bar; >>>> } >>>> >>>> Assuming there is no other code modifying m_bar, foo->bar()->method() is >>>> always safe to call even if method wasn’t a trivial function. Right now, >>>> static analyzer doesn’t recognize this pattern so we’d be forced to write >>>> code like this: foo->protectedBar()->method() where ensureProtectedBar is >>>> a wrapper around ensureBar which returns Ref<Bar>. >>>> >>>> A suggestion was made that static analyzer can recognize this patten. >>>> Specifically, if we introduced a new smart pointer types that only allow >>>> setting the value once, static analyzer can allow foo->bar()->method()and >>>> avoid ref-churn in some cases: >>>> >>>> e.g. >>>> >>>> class Foo { >>>> Bar& bar() { >>>> if (!m_bar) >>>> m_bar = Bar::create(); >>>> return *m_bar; >>>> } >>>> >>>> SetOnceRefPtr<Bar> m_bar; >>>> } >>>> >>>> SetOnceRefPtr::operator=(T*) release asserts that m_ptr isn’t set, and >>>> doesn’t have a move constructor, operator=(nullptr_t), leakRef(), >>>> releaseNonNull(), etc… which can override the value of m_ptr after setting >>>> the value via operator= or in constructor. >>>> >>>> We could create various variants: SetOnceRef, SetOnceUniquePtr, >>>> SetOnceUniqueRef. >>>> >>>> Do you think this will be useful? >>>> >>>> - R. Niwa >>> >>> >>> _______________________________________________ >>> webkit-dev mailing list >>> webkit-dev@lists.webkit.org >>> https://lists.webkit.org/mailman/listinfo/webkit-dev >> >> _______________________________________________ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> https://lists.webkit.org/mailman/listinfo/webkit-dev > > _______________________________________________ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
