https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96145
Bug ID: 96145
Summary: Weird output in compiling a typedef union as a
function return type
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haoxintu at gmail dot com
Target Milestone: ---
Hi, all.
This code, test.cc, uses a typedef name of a union as a return type of a
function, the GCC compiled output might be weird.
$cat test.cc
typedef union{} typedef_union;
typename :: typedef_union foo1 () {}
$g++ -w test.cc
test.cc:2:13: error: 'class' tag used in naming 'union typedef_union'
[-fpermissive]
2 | typename :: typedef_union foo1 () {}
| ^~~~~~~~~~~~~
test.cc:1:17: note: 'union typedef_union' was previously declared here
1 | typedef union{} typedef_union;
| ^~~~~~~~~~~~~
Two things might be weird:
1. This code is a valid code I guess. Other mainstream compilers (I test this
in clang, ice, and mvsc) accept this by default, although the error can
disappear when adding "-fpermissive" option. Maybe is this a reject-valid
issue?
2. The output "class" tag is wrong. I don't use the "class" keyword in this
small code. Maybe is this a diagnostic issue?
I report this because of the related discussions in llvm:
https://bugs.llvm.org/show_bug.cgi?id=46645
Every version from 4.0 onwards behaves the same (I didn't test anything older).
Thanks,
Haoxin
