[clang] [clang] Introduce [[clang::lifetime_capture_by(X)]] (PR #111499)

[Haojian Wu via cfe-commits]

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+// RUN: %clang_cc1 -std=c++23 -verify %s
+
+struct S {
+  const int *x;
+  void captureInt(const int&x [[clang::lifetime_capture_by(this)]]) { this->x = &x; }
+};
+
+///////////////////////////
+// Test for valid usages.
+///////////////////////////
+[[clang::lifetime_capture_by(unknown)]] // expected-error {{'lifetime_capture_by' attribute only applies to parameters and implicit object parameters}}
+void nonMember(
+    const int &x1 [[clang::lifetime_capture_by(s, t)]],
+    S &s,
+    S &t,
+    const int &x2 [[clang::lifetime_capture_by(12345 + 12)]], // expected-error {{'lifetime_capture_by' attribute argument 12345 + 12 is not a known function parameter. Must be a function parameter of one of 'this', 'global' or 'unknown'}}
+    const int &x3 [[clang::lifetime_capture_by(abcdefgh)]],   // expected-error {{'lifetime_capture_by' attribute argument 'abcdefgh' is not a known function parameter. Must be a function parameter of one of 'this', 'global' or 'unknown'}}
+    const int &x4 [[clang::lifetime_capture_by("abcdefgh")]], // expected-error {{'lifetime_capture_by' attribute argument "abcdefgh" is not a known function parameter. Must be a function parameter of one of 'this', 'global' or 'unknown'}}
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hokein wrote:

The diagnostic messages in the test are not updated.

https://github.com/llvm/llvm-project/pull/111499