[llvm-branch-commits] [clang] [clang] Introduce scopes for arguments without destructors (PR #191019)

[Eli Friedman via llvm-branch-commits]

================
@@ -6872,6 +6893,15 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType,
   assert(CalleeType->isFunctionPointerType() &&
          "Call must have function pointer type!");
 
+  // For calls with trivial aggregate arguments, we want to tighten the
+  // lifetime of those aggregates to end immediately after the call returns,
+  // rather than at the end of the full-expression. We create a nested cleanup
+  // scope to intercept these lifetime markers. However, we only do this if the
+  // call is "safe".
----------------
efriedma-quic wrote:

Consider:

```
struct S { int x; };
const int* f(const int* p) { return p; }
int g() {
  return *f(&((const S&)S{2}).x);
}
```

The lifetime should last to the end of the full-expression.  Scanning the argument types clearly won't catch this.  Scanning the arguments is probably possible, but maybe tricky to get right.

https://github.com/llvm/llvm-project/pull/191019