[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[Doug Wyatt via cfe-commits]

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+// RUN: %clang_cc1 -fsyntax-only -fblocks -fcxx-exceptions -verify %s
+// RUN: %clang_cc1 -fsyntax-only -fblocks -verify -x c -std=c23 %s
+
+#if !__has_attribute(nonblocking)
+#error "the 'nonblocking' attribute is not available"
+#endif
+
+// --- ATTRIBUTE SYNTAX: SUBJECTS ---
+
+int nl_var [[clang::nonblocking]]; // expected-warning {{'nonblocking' only applies to function types; type here is 'int'}}
+struct nl_struct {} [[clang::nonblocking]]; // expected-warning {{attribute 'nonblocking' is ignored, place it after "struct" to apply attribute to type declaration}}
+struct [[clang::nonblocking]] nl_struct2 {}; // expected-error {{'nonblocking' attribute cannot be applied to a declaration}}
+
+// Positive case
+typedef void (*fo)() [[clang::nonblocking]];
+void (*read_me_and_weep(
+  int val, void (*func)(int) [[clang::nonblocking]])
+  [[clang::nonblocking]]) (int)
+  [[clang::nonblocking]];
+
+// --- ATTRIBUTE SYNTAX: ARGUMENT COUNT ---
+void nargs_1() [[clang::nonblocking(1, 2)]];  // expected-error {{'nonblocking' attribute takes no more than 1 argument}}
+void nargs_2() [[clang::nonallocating(1, 2)]]; // expected-error {{'nonallocating' attribute takes no more than 1 argument}}
+void nargs_3() [[clang::blocking(1)]]; // expected-error {{'blocking' attribute takes no arguments}}
+void nargs_4() [[clang::allocating(1)]]; // expected-error {{'allocating' attribute takes no arguments}}
+
+// --- ATTRIBUTE SYNTAX: COMBINATIONS ---
+// Check invalid combinations of nonblocking/nonallocating attributes
+
+void nl_true_false_1() [[clang::nonblocking(true)]] [[clang::blocking]]; // expected-error {{'blocking' and 'nonblocking' attributes are not compatible}}
+void nl_true_false_2() [[clang::blocking]] [[clang::nonblocking(true)]]; // expected-error {{'nonblocking' and 'blocking' attributes are not compatible}}
+
+void na_true_false_1() [[clang::nonallocating(true)]] [[clang::allocating]]; // expected-error {{'allocating' and 'nonallocating' attributes are not compatible}}
+void na_true_false_2() [[clang::allocating]] [[clang::nonallocating(true)]]; // expected-error {{'nonallocating' and 'allocating' attributes are not compatible}}
+
+void nl_true_na_true_1() [[clang::nonblocking]] [[clang::nonallocating]];
+void nl_true_na_true_2() [[clang::nonallocating]] [[clang::nonblocking]];
+
+void nl_true_na_false_1() [[clang::nonblocking]] [[clang::allocating]]; // expected-error {{'allocating' and 'nonblocking' attributes are not compatible}}
+void nl_true_na_false_2() [[clang::allocating]] [[clang::nonblocking]]; // expected-error {{'nonblocking' and 'allocating' attributes are not compatible}}
+
+void nl_false_na_true_1() [[clang::blocking]] [[clang::nonallocating]];
+void nl_false_na_true_2() [[clang::nonallocating]] [[clang::blocking]];
+
+void nl_false_na_false_1() [[clang::blocking]] [[clang::allocating]];
+void nl_false_na_false_2() [[clang::allocating]] [[clang::blocking]];
+
+// --- TYPE CONVERSIONS ---
+
+void unannotated();
+void nonblocking() [[clang::nonblocking]];
+void nonallocating() [[clang::nonallocating]];
+void type_conversions()
+{
+  // It's fine to remove a performance constraint.
+  void (*fp_plain)();
+
+  fp_plain = nullptr;
+  fp_plain = unannotated;
+  fp_plain = nonblocking;
+  fp_plain = nonallocating;
+
+  // Adding/spoofing nonblocking is unsafe.
+  void (*fp_nonblocking)() [[clang::nonblocking]];
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dougsonos wrote:

done

https://github.com/llvm/llvm-project/pull/84983