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

[Boaz Brickner via llvm-commits]

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@@ -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]]);
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bricknerb wrote:

My 2cs are that these are actually not test helper functions, they're input to the test.
You happen to need similar inputs in multiple tests so you define the inputs once.
I believe this makes tests harder to read and maintain.
I agree that someone familiar with these tests would find their name indicative, but for me it took some time to remember what each means.
If we simply copy them it seems they would actually be copied ~3 times, and then we can actually consider if each usage of them adds coverage.

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