[Bug c++/60955] Erroneous warning about taking address of register with std=c++1y

["manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60955

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-04-26
                 CC|                            |manu at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Harald van Dijk from comment #2)
> This is caused by the implementation of C++1y decltype(auto), where
> seemingly redundant parentheses around an identifier must not simply be
> removed, because they may be significant.
> 
> int a;
> decltype(auto) b = a; // means int b = a;
> decltype(auto) c = (a); // means int &c = a;
> 
> GCC implements this by transforming (a) into static_cast<int &>(a)
> (force_paren_expr in gcc/cp/semantics.c), which would normally be a no-op,
> but causes the warning when a is declared using the "register" keyword.

It is pretty awful that C++14 has made extra parentheses to become significant.

But yes, this explains this bug and also PR57573.

It would be nice if expressions could be marked as compiler-generated, like we
have DECL_ARTIFICIAL for declarations. But you could set TREE_NO_WARNING(expr)
= true and check that in the warning code.
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Subject: [Bug c++/60955] Erroneous warning about taking address of register with std=c++1y
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60955

--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
Perhaps also this special case could also be removed by using TREE_NO_WARNING.

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index c91612c..d8374d9 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -6291,7 +6291,10 @@ maybe_warn_about_useless_cast (tree type, tree expr,
tsubst_flags_t complain)
   if (warn_useless_cast
       && complain & tf_warning)
     {
-      if (REFERENCE_REF_P (expr))
+      /* In C++14 mode, this interacts badly with force_paren_expr.  And it
+     isn't necessary in any mode, because the code below handles
+     glvalues properly.  For 4.9, just skip it in C++14 mode.  */
+      if (cxx_dialect < cxx1y && REFERENCE_REF_P (expr))
     expr = TREE_OPERAND (expr, 0);
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Subject: [Bug libfortran/52539] I/O: Wrong result for UTF-8/UCS-4 list-directed and namelist read and nml write
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idR539

--- Comment #7 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
Author: jvdelisle
Date: Sat Apr 26 21:52:26 2014
New Revision: 209828

URL: http://gcc.gnu.org/viewcvs?rev 9828&root=gcc&view=rev
Log:
2014-04-26  Jerry DeLisle  <jvdelisle@gcc.gnu>

    PR libfortran/52539
    * io/list_read.c: Add uchar typedef. (push_char4): New function
    to save kind=4 character. (next_char_utf8): New function to read
    a single UTF-8 encoded character value. (read_chracter): Update
    to use the new functions for reading UTF-8 strings.
    (list_formatted_read_scalar): Update to handle list directed
    reads of UTF-8 strings. (nml_read_obj): Likewise update for
    UTF-8 strings in namelists.
    * io/write.c (nml_write_obj): Add kind=4 character support for
    namelist writes.

Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/list_read.c
    trunk/libgfortran/io/write.c