[Bug c++/39028] New: C++ front-end rejects "__label__" at the beginning of a block after "for" and "while"

["springl-gcc at bfw-online dot de" <gcc-bugzilla at gcc dot gnu dot org>]

Trying to compile the c++ program label.C

void c ()
{ for (;;)   {__label__ l; goto l; l:;}
  while (1)  {__label__ l; goto l; l:;}
  if (1)     {__label__ l; goto l; l:;}
  do         {__label__ l; goto l; l:;} while (1);
             {__label__ l; goto l; l:;}
}

using
  g++ -Wall -Wextra   -c label.C
with g++ versions 4.4.0 20090129 (experimental) and 4.3.3 gives:

label.C: In function 'void c()':
label.C:2: error: '__label__' not at the beginning of a block
label.C:3: error: '__label__' not at the beginning of a block
label.C:3: error: duplicate label 'l'

The fix for bug 32121 "C++ front-end accepts invalid __label__
declarations" (svn revision 129253) moved handling __label__ declarations
to function cp_parser_compound_statement in gcc/cp/parser.c and omitted
it in function cp_parser_already_scoped_statement.  The newly introduced
tests cases only check the error case for while and for statements,
unfortunately.

Without any deeper understanding of gcc internals, I suggest two
possible fixes:

- copy the two lines handling __label__ declarations
from function cp_parser_compound_statement to function
cp_parser_already_scoped_statement, which might be the smallest change or
- merge part of cp_parser_already_scoped_statement's functionality to
cp_parser_compound_statement avoiding code duplication.


-- 
           Summary: C++ front-end rejects "__label__" at the beginning of a
                    block after "for" and "while"
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: springl-gcc at bfw-online dot de
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39028