[clang] [llvm] [clang] Implement lifetime analysis for lifetime_capture_by(X) (PR #115921)

[Utkarsh Saxena via cfe-commits]

================
@@ -0,0 +1,348 @@
+// RUN: %clang_cc1 --std=c++20 -fsyntax-only -Wdangling -Wdangling-field -Wreturn-stack-address -verify %s
+
+#include "Inputs/lifetime-analysis.h"
+
+struct X {
+  const int *x;
+};
+X x;
+
+// ****************************************************************************
+// Capture an integer
+// ****************************************************************************
+namespace capture_int {
+void captureInt(const int &i [[clang::lifetime_capture_by(x)]], X &x);
+void captureRValInt(int &&i [[clang::lifetime_capture_by(x)]], X &x);
+void noCaptureInt(int i [[clang::lifetime_capture_by(x)]], X &x);
+
+void use() {
+  int local;
+  captureInt(1, // expected-warning {{object whose reference is captured by 'x' will be destroyed at the end of the full-expression}}
+            x);
+  captureRValInt(1, x); // expected-warning {{object whose reference is captured by 'x'}}
+  captureInt(local, x);
+  noCaptureInt(1, x);
+  noCaptureInt(local, x);
+}
+} // namespace capture_int
+
+// ****************************************************************************
+// Capture std::string (gsl owner types)
+// ****************************************************************************
+std::string_view getLifetimeBoundView(const std::string& s [[clang::lifetimebound]]);
+std::string_view getNotLifetimeBoundView(const std::string& s);
+const std::string& getLifetimeBoundString(const std::string &s [[clang::lifetimebound]]);
+const std::string& getLifetimeBoundString(std::string_view sv [[clang::lifetimebound]]);
----------------
usx95 wrote:

I think the name now are quite verbose and self explanatory which reduces the need to go to the definition.
Helper functions in tests are not uncommon. Duplicating them to almost all the usages (which are almost all tests) doesn't make sense to me.

Moved it to a separate section of the file.

https://github.com/llvm/llvm-project/pull/115921