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

[Utkarsh Saxena via cfe-commits]

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@@ -0,0 +1,220 @@
+// 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;
+  void captureInt(const int& x [[clang::lifetime_capture_by(this)]]) { this->x = &x; }
+  void captureSV(std::string_view sv [[clang::lifetime_capture_by(this)]]);
+};
+///////////////////////////
+// Detect dangling cases.
+///////////////////////////
+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);
+
+std::string_view substr(const std::string& s [[clang::lifetimebound]]);
+std::string_view strcopy(const std::string& s);
+
+void captureSV(std::string_view s [[clang::lifetime_capture_by(x)]], X &x);
+void captureRValSV(std::string_view &&sv [[clang::lifetime_capture_by(x)]], X &x);
+void noCaptureSV(std::string_view sv, X &x);
+void captureS(const std::string &s [[clang::lifetime_capture_by(x)]], X &x);
+void captureRValS(std::string &&s [[clang::lifetime_capture_by(x)]], X &x);
+
+const std::string& getLB(const std::string &s [[clang::lifetimebound]]);
+const std::string& getLB(std::string_view sv [[clang::lifetimebound]]);
+const std::string* getPointerLB(const std::string &s [[clang::lifetimebound]]);
+const std::string* getPointerNoLB(const std::string &s);
+
+void capturePointer(const std::string* sp [[clang::lifetime_capture_by(x)]], X &x);
+
+struct ThisIsCaptured {
+  void capture(X &x) [[clang::lifetime_capture_by(x)]];
+};
+
+void captureByGlobal(std::string_view s [[clang::lifetime_capture_by(global)]]);
+void captureByUnknown(std::string_view s [[clang::lifetime_capture_by(unknown)]]);
+
+void use() {
+  std::string_view local_sv;
+  std::string local_s;
+  X x;
+  // Capture an 'int'.
+  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);
+
+  // Capture using std::string_view.
+  captureSV(local_sv, x);
+  captureSV(std::string(), // expected-warning {{object whose reference is captured by 'x'}}
+            x);
+  captureSV(substr(
+      std::string() // expected-warning {{object whose reference is captured by 'x'}}
+      ), x);
+  captureSV(substr(local_s), x);
+  captureSV(strcopy(std::string()), x);
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usx95 wrote:

Done.

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