58 lines · c
1// RUN: %clang_cc1 -verify -std=c2y -pedantic -Wno-unused %s2// RUN: %clang_cc1 -verify=expected,pre-c2y -std=c2y -Wpre-c2y-compat -Wno-unused %s3// RUN: %clang_cc1 -verify=expected,ext -std=c23 -pedantic -Wno-unused %s4 5/* WG14 N3409: Clang 216 * Slay Some Earthly Demons X7 *8 * Removes the requirement that an expression with type void cannot be used in9 * any way. This was making it UB to use a void expression in a _Generic10 * selection expression for no good reason, as well as making it UB to cast a11 * void expression to void, etc.12 */13 14extern void x;15void foo() {16 // FIXME: this is technically an extension before C2y and should be diagnosed17 // under -pedantic.18 (void)(void)1;19 // FIXME: same with this.20 x;21 _Generic(x, void: 1); /* pre-c2y-warning {{use of incomplete type 'void' in a '_Generic' association is incompatible with C standards before C2y}}22 ext-warning {{incomplete type 'void' in a '_Generic' association is a C2y extension}}23 */24 _Generic(x, typeof(x): 1); /* pre-c2y-warning {{use of incomplete type 'typeof (x)' (aka 'void') in a '_Generic' association is incompatible with C standards before C2y}}25 ext-warning {{incomplete type 'typeof (x)' (aka 'void') in a '_Generic' association is a C2y extension}}26 */27 (void)_Generic(void, default : 1); /* pre-c2y-warning {{passing a type argument as the first operand to '_Generic' is incompatible with C standards before C2y}}28 ext-warning {{passing a type argument as the first operand to '_Generic' is a C2y extension}}29 */30 31 // This is not sufficiently important of an extension to warrant a "not32 // compatible with standards before C2y" warning, but it is an extension in33 // C23 and earlier.34 return x; // ext-warning {{void function 'foo' should not return void expression}}35}36 37 38// Ensure we behave correctly with incomplete types. See GH141549.39static_assert(40 _Generic(41 void, /* ext-warning {{passing a type argument as the first operand to '_Generic' is a C2y extension}}42 pre-c2y-warning {{passing a type argument as the first operand to '_Generic' is incompatible with C standards before C2y}}43 */44 void : 1,45 default : 046 )47);48 49static_assert(50 _Generic( // expected-error {{static assertion failed}}51 12,52 void : 1, /* ext-warning {{incomplete type 'void' in a '_Generic' association is a C2y extension}}53 pre-c2y-warning {{use of incomplete type 'void' in a '_Generic' association is incompatible with C standards before C2y}}54 */55 default : 056 )57);58