[Bug c++/66900] New: No error message for ill-formed program with qualified name lookup

[Bug c++/66900] New: No error message for ill-formed program with qualified name lookup

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66900

            Bug ID: 66900
           Summary: No error message for ill-formed program with qualified
                    name lookup
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anders.granlund.0 at gmail dot com
  Target Milestone: ---

Created attachment 35998
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35998&action=edit
prog.cc used in the command line

Compiled the attached ill-formed program with the following command line:

gcc prog.cc

It compiles without error. The expected behaviour is to get an error message
since the program is ill-formed by basic.lookup.qual]p1:

"... If a :: scope resolution operator in a nested-name-specifier is not
preceded by a decltype-specifier, lookup of the name preceding that ::
considers only namespaces, types, and templates whose specializations are
types. If the name found does not designate a namespace or a class,
enumeration, or dependent type, the program is ill-formed. ..."

http://eel.is/c++draft/basic.lookup.qual#1

For comparison Clang gives a compiler error.

Output for gcc -v:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.2-19ubuntu1'
--with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)

[Bug c++/66900] No error message for ill-formed program with qualified name lookup

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66900

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=26950
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-08-26
           Keywords|                            |accepts-invalid

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
>From the attachment:

namespace N {
    int j = 1;
}

namespace M {
    typedef int N;
    void f() {
        N::j = 2;
    }
}

int main() { M::f(); }