Author: Aaron Ballman Date: 2025-03-07T09:37:15-05:00 New Revision: 40ee5a0bcc333f2df5427bfaba73f2dc83c0ae19
URL: https://github.com/llvm/llvm-project/commit/40ee5a0bcc333f2df5427bfaba73f2dc83c0ae19 DIFF: https://github.com/llvm/llvm-project/commit/40ee5a0bcc333f2df5427bfaba73f2dc83c0ae19.diff LOG: [C2y] Claim conformance to WG14 N3481 This paper made it a constraint violation to have an incomplete type during lvalue conversion. Previously, this was undefined behavior. Clang has always diagnosed this for non-void incomplete types. However, Clang does allow derefencing a void pointer (with a diagnostic, so we still meet the conformance requirements), but not for a value computation. Added: clang/test/C/C2y/n3481.c Modified: clang/www/c_status.html Removed: ################################################################################ diff --git a/clang/test/C/C2y/n3481.c b/clang/test/C/C2y/n3481.c new file mode 100644 index 0000000000000..1088b62dd8085 --- /dev/null +++ b/clang/test/C/C2y/n3481.c @@ -0,0 +1,23 @@ +// RUN: %clang_cc1 -verify -std=c2y %s +// RUN: %clang_cc1 -verify -std=c23 %s + +/* WG14 N3481: Yes + * Slay Some Earthly Demons XVI + * + * It was previously UB to use a non-array lvalue with an incomplete type in a + * context which required the value of the object. Clang has always diagnosed + * this as an error, except when the incomplete type is void. Then we allow the + * dereference, but not for a value computation. + */ + +struct f *p; // expected-note {{forward declaration of 'struct f'}} +void g(void) { + (void)*p; // expected-error {{incomplete type 'struct f' where a complete type is required}} +} + +void h(void *ptr) { + (void)*ptr; // expected-warning {{ISO C does not allow indirection on operand of type 'void *'}} + (*ptr)++; /* expected-warning {{ISO C does not allow indirection on operand of type 'void *'}} + expected-error {{cannot increment value of type 'void'}} + */ +} diff --git a/clang/www/c_status.html b/clang/www/c_status.html index b198053ece041..b72b96dd598b5 100644 --- a/clang/www/c_status.html +++ b/clang/www/c_status.html @@ -309,7 +309,7 @@ <h2 id="c2y">C2y implementation status</h2> <tr> <td>Slay Some Earthly Demons XVI</td> <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3481.pdf";>N3481</a></td> - <td class="unknown" align="center">Unknown</td> + <td class="full" align="center">Yes</td> </tr> <tr> <td>Slay Some Earthly Demons XVII</td> _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
