https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113919
Bug ID: 113919 Summary: Nested anonymous unions should be prohibited in ISO C++ Product: gcc Version: 13.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: tsqurt at outlook dot com Target Milestone: --- Created attachment 57425 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57425&action=edit example.cpp Anonymous unions shall not be declared within an anonymous union. But gcc never warns about this. Demo source code as a C++17 source file attached. Note: attached code is a valid C source code but not a valid C++ source code. GCC is expected to REJECT or WARN, but it compiles without any message. $gcc example.cpp -std=c++17 --pedantic -Wall -Wextra expect: warning: ISO C++ prohibits anonymous unions within anonymous unions[-Wpedantic] But gcc exited with code 0, leaving empty message. Reference: N4849, Working Draft, Standard for Programming Language C++, Chapter 11, Section 5.1 Anonymous unions. (Different versions of modern C++ specification mention this issue in their correspondent chapters.)