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// RUN: %clang_cc1 -verify -std=c2y -pedantic -Wno-unused %s
// RUN: %clang_cc1 -verify=expected,pre-c2y -std=c2y -Wpre-c2y-compat -Wno-unused %s
// RUN: %clang_cc1 -verify=expected,ext -std=c23 -pedantic -Wno-unused %s
/* WG14 N3409: Clang 21
* Slay Some Earthly Demons X
*
* Removes the requirement that an expression with type void cannot be used in
* any way. This was making it UB to use a void expression in a _Generic
* selection expression for no good reason, as well as making it UB to cast a
* void expression to void, etc.
*/
extern void x;
void foo() {
// FIXME: this is technically an extension before C2y and should be diagnosed
// under -pedantic.
(void)(void)1;
// FIXME: same with this.
x;
_Generic(x, void: 1); /* pre-c2y-warning {{use of incomplete type 'void' in a '_Generic' association is incompatible with C standards before C2y}}
ext-warning {{incomplete type 'void' in a '_Generic' association is a C2y extension}}
*/
_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}}
ext-warning {{incomplete type 'typeof (x)' (aka 'void') in a '_Generic' association is a C2y extension}}
*/
(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}}
ext-warning {{passing a type argument as the first operand to '_Generic' is a C2y extension}}
*/
// This is not sufficiently important of an extension to warrant a "not
// compatible with standards before C2y" warning, but it is an extension in
// C23 and earlier.
return x; // ext-warning {{void function 'foo' should not return void expression}}
}
// Ensure we behave correctly with incomplete types. See GH141549.
static_assert(
_Generic(
void, /* ext-warning {{passing a type argument as the first operand to '_Generic' is a C2y extension}}
pre-c2y-warning {{passing a type argument as the first operand to '_Generic' is incompatible with C standards before C2y}}
*/
void : 1,
default : 0
)
);
static_assert(
_Generic( // expected-error {{static assertion failed}}
12,
void : 1, /* ext-warning {{incomplete type 'void' in a '_Generic' association is a C2y extension}}
pre-c2y-warning {{use of incomplete type 'void' in a '_Generic' association is incompatible with C standards before C2y}}
*/
default : 0
)
);
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