In discussion of jakub's patch for C++20 pointer-interconvertibility, it came up that we allow anonymous structs to have bases, but don't do anything usable with them. Let's reject it.
The comment change is something I noticed while looking for the right place to diagnose this: finish_struct_anon does not actually check for anything invalid, so it shouldn't claim to. Tested x86_64-pc-linux-gnu, applying to trunk. gcc/cp/ChangeLog: * class.c (finish_struct_anon): Improve comment. * decl.c (fixup_anonymous_aggr): Reject anonymous struct with bases. gcc/testsuite/ChangeLog: * g++.dg/ext/anon-struct8.C: New test. --- gcc/cp/class.c | 3 +-- gcc/cp/decl.c | 3 +++ gcc/testsuite/g++.dg/ext/anon-struct8.C | 9 +++++++++ 3 files changed, 13 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/ext/anon-struct8.C diff --git a/gcc/cp/class.c b/gcc/cp/class.c index 14db06692dc..6f31700c06c 100644 --- a/gcc/cp/class.c +++ b/gcc/cp/class.c @@ -3072,8 +3072,7 @@ finish_struct_anon_r (tree field) } } -/* Check for things that are invalid. There are probably plenty of other - things we should check for also. */ +/* Fix up any anonymous union/struct members of T. */ static void finish_struct_anon (tree t) diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 01d64a16125..71308a06c63 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -5084,6 +5084,9 @@ fixup_anonymous_aggr (tree t) { tree field, type; + if (BINFO_N_BASE_BINFOS (TYPE_BINFO (t))) + error_at (location_of (t), "anonymous struct with base classes"); + for (field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field)) if (TREE_CODE (field) == FIELD_DECL) { diff --git a/gcc/testsuite/g++.dg/ext/anon-struct8.C b/gcc/testsuite/g++.dg/ext/anon-struct8.C new file mode 100644 index 00000000000..f4e3f11b678 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/anon-struct8.C @@ -0,0 +1,9 @@ +// { dg-options "" } + +struct A { }; +struct B { + struct: A { int i; }; // { dg-error "anonymous struct with base" } +}; +union U { + struct: A { int i; }; // { dg-error "anonymous struct with base" } +}; base-commit: 0ba2003cf306aa98b6ec91c9d849ab9bafcf17c2 -- 2.27.0