[clang] nonblocking/nonallocating attributes: 2nd pass caller/callee analysis (PR #99656)

[via cfe-commits]

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+// RUN: %clang_cc1 -fsyntax-only -fblocks -fcxx-exceptions -std=c++20 -verify %s
+// These are in a separate file because errors (e.g. incompatible attributes) currently prevent
+// the FXAnalysis pass from running at all.
+
+// This diagnostic is re-enabled and exercised in isolation later in this file.
+#pragma clang diagnostic ignored "-Wperf-constraint-implies-noexcept"
+
+// --- CONSTRAINTS ---
+
+void nb1() [[clang::nonblocking]]
+{
+	int *pInt = new int; // expected-warning {{'nonblocking' function must not allocate or deallocate memory}}
+	delete pInt; // expected-warning {{'nonblocking' function must not allocate or deallocate memory}}
+}
+
+void nb2() [[clang::nonblocking]]
+{
+	static int global; // expected-warning {{'nonblocking' function must not have static locals}}
+}
+
+void nb3() [[clang::nonblocking]]
+{
+	try {
+		throw 42; // expected-warning {{'nonblocking' function must not throw or catch exceptions}}
+	}
+	catch (...) { // expected-warning {{'nonblocking' function must not throw or catch exceptions}}
+	}
+}
+
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Sirraide wrote:

> a narrower approach would be to note the extra context of being inside an initializer when a violation is generated from a constructor, and add that context to the diagnostic.

I think that sounds more or less like what I had in mind. The main things I was concerned about were
1. We should compltain that an initialiser is e.g. blocking iff the constructor in question actually executes that initialiser, and
2. *Ideally*, it should be obvious to the user—by whatever means—that the problem is in the initaliser.

https://github.com/llvm/llvm-project/pull/99656