From e7300e75b51a7e7d4e81975b4be7a6c65f9a8286 Mon Sep 17 00:00:00 2001 From: Aaron Ballman Date: Wed, 18 Jan 2023 08:49:45 -0500 Subject: Diagnose extensions in 'offsetof' https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm made very clear that it is an UB having type definitions with in offsetof. Clang supports defining a type as the first argument as a conforming extension due to how many projects use the construct in C99 and earlier to calculate the alignment of a type. GCC also supports defining a type as the first argument. This adds extension warnings and documentation for the functionality Clang explicitly supports. Fixes #57065 Reverts the revert of 39da55e8f548a11f7dadefa73ea73d809a5f1729 Co-authored-by: Yingchi Long Co-authored-by: Aaron Ballman Differential Revision: https://reviews.llvm.org/D133574 --- clang/test/CodeGen/offsetof.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'clang/test/CodeGen/offsetof.c') diff --git a/clang/test/CodeGen/offsetof.c b/clang/test/CodeGen/offsetof.c index c279e22..13b34ea 100644 --- a/clang/test/CodeGen/offsetof.c +++ b/clang/test/CodeGen/offsetof.c @@ -10,3 +10,7 @@ int test(int len) { return __builtin_offsetof(struct sockaddr_un, sun_path[len+1]); } +// Ensure we can form the offset to a structure defined in the first argument +// without crashing or asserting on an invalid declaration (because the +// declaration is actually valid). +void c() { __builtin_offsetof(struct {int b;}, b); } -- cgit v1.1