flx added inline comments.
================
Comment at:
clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp:98-101
auto Matches =
match(findAll(declStmt(has(varDecl(equalsNode(&InitializingVar))))
.bind("declStmt")),
+ Body, Context);
----------------
ymandel wrote:
> Consider inspecting the `DeclContext`s instead, which should be much more
> efficient than searching the entire block. Pass the `FunctionDecl` as an
> argument instead of `Body`, since it is a `DeclContext`. e.g. `const
> DeclContext &Fun`
>
> Then, either
> 1. Call `Fun.containsDecl(InitializingVar)`, or
> 2. Search through the contexts yourself; something like:
> ```
> DeclContext* DC = InitializingVar->getDeclContext();
> while (DC != nullptr && DC != &Fun)
> DC = DC->getLexicalParent();
> if (DC == nullptr)
> // The reference or pointer is not initialized anywhere witin the function.
> We
> // assume its pointee is not modified then.
> return true;
> ```
Are #1 and #2 equivalent? From the implementation and comment I cannot tell
whether #1 would cover cases where the variable is not declared directly in the
function, but in child block:
```
void Fun() {
{
var i;
{
i.usedHere();
}
}
}
```
I'm also reading this as an optimization to more quickly determine whether we
can stop here. We still need to find the matches for the next steps, but I
think I could then limit matching to the DeclContext I found here. Is this
correct? For this I would actually need the DeclContext result from #2.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D103021/new/
https://reviews.llvm.org/D103021
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