[PATCH] D139737: [-Wunsafe-buffer-usage] Initiate Fix-it generation for local variable declarations

[Ziqing Luo via Phabricator via cfe-commits]

ziqingluo-90 marked 8 inline comments as done.
ziqingluo-90 added inline comments.


================
Comment at: clang/lib/Analysis/UnsafeBufferUsage.cpp:637
 
-static Strategy
-getNaiveStrategy(const llvm::SmallVectorImpl<const VarDecl *> &UnsafeVars) {
----------------
NoQ wrote:
> Hmm, did this need to be moved? I don't think you're calling this function from the new code.
it does look like I moved it.  Will change it back.


================
Comment at: clang/lib/Analysis/UnsafeBufferUsage.cpp:780-781
+  } else {
+    // In cases `Init` is of the form `&Var` after stripping of implicit
+    // casts, where `&` is the built-in operator, the extent is 1.
+    if (auto AddrOfExpr = dyn_cast<UnaryOperator>(Init->IgnoreImpCasts()))
----------------
NoQ wrote:
> ```lang=c
> int x = 1;
> char *ptr = &x; // std::span<char> ptr { &x, 4 };
> ```
> This is valid code. I suspect we want to check types as well, to see that type sizes match.
> 
> Most of the time code like this violates strict aliasing, but `char` is exceptional, and even if it did violate strict aliasing, people can compile with `-fno-strict-aliasing` to define away the UB, so we have to respect that.
This code is not valid in C++.  An explicit cast is needed in front of `&x`.  I will add a test to show that 

```
int x = 1;
char * ptr = (char *)&x;
```
will have a place holder for the span size.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139737/new/

https://reviews.llvm.org/D139737