[Bug c++/61760] -Wconversion inconsistency between gcc and g++

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61760

Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-07-09
                 CC|                            |manu at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> ---
The C FE produces:

 <nop_expr 0x7ffff751dfe0
    type <integer_type 0x7ffff740a690 int public SI
        size <integer_cst 0x7ffff74088b8 constant 32>
        unit size <integer_cst 0x7ffff74088d0 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0x7ffff740a690 precision
32 min <integer_cst 0x7ffff7408870 -2147483648> max <integer_cst 0x7ffff7408888
2147483647>
        pointer_to_this <pointer_type 0x7ffff7415738>>

    arg 0 <rshift_expr 0x7ffff750eac8
        type <integer_type 0x7ffff740a3f0 unsigned char public unsigned
string-flag QI
            size <integer_cst 0x7ffff7408768 constant 8>
            unit size <integer_cst 0x7ffff7408780 constant 1>
            align 8 symtab 0 alias set -1 canonical type 0x7ffff740a3f0
precision 8 min <integer_cst 0x7ffff7408798 0> max <integer_cst 0x7ffff7408738
255>>

        arg 0 <parm_decl 0x7ffff7531000 x type <integer_type 0x7ffff740a3f0
unsigned char>
            used unsigned QI file /home/manuel/test.c line 1 col 33 size
<integer_cst 0x7ffff7408768 8> unit size <integer_cst 0x7ffff7408780 1>
            align 8 context <function_decl 0x7ffff7514700 foo> arg-type
<integer_type 0x7ffff740a3f0 unsigned char>>
        arg 1 <integer_cst 0x7ffff7408a20 constant 1>>
    /home/manuel/test.c:3:12>

that is (int) (x >> 1).

The C++ FE produces:

 <rshift_expr 0x7ffff75603e8
    type <integer_type 0x7ffff740a690 int public SI
        size <integer_cst 0x7ffff7408a68 constant 32>
        unit size <integer_cst 0x7ffff7408a80 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0x7ffff740a690 precision
32 min <integer_cst 0x7ffff7408a20 -2147483648> max <integer_cst 0x7ffff7408a38
2147483647>
        pointer_to_this <pointer_type 0x7ffff741c738>>

    arg 0 <nop_expr 0x7ffff7576220 type <integer_type 0x7ffff740a690 int>

        arg 0 <parm_decl 0x7ffff7577080 x type <integer_type 0x7ffff740a3f0
unsigned char>
            used unsigned QI file /home/manuel/test.c line 1 col 33
            size <integer_cst 0x7ffff7408918 constant 8>
            unit size <integer_cst 0x7ffff7408930 constant 1>
            align 8 context <function_decl 0x7ffff7567b00 foo>
            arg-type <integer_type 0x7ffff740a690 int>>>
    arg 1 <integer_cst 0x7ffff7408bd0 type <integer_type 0x7ffff740a690 int>
constant 1>
    /home/manuel/test.c:3:12>

that is (((int)x) >> 1)

I am not sure which one is more correct, but the latter prevents
unsafe_conversion_p from seeing that the implicit conversion cannot alter the
value.