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Re: [patch]: Address const warnings in gimple.h
On Wed, Jun 9, 2010 at 2:57 PM, Kai Tietz <ktietz70@googlemail.com> wrote:
> 2010/6/9 Richard Guenther <richard.guenther@gmail.com>:
>> On Wed, Jun 9, 2010 at 2:41 PM, Kai Tietz <Kai.Tietz@onevision.com> wrote:
>>> Hello,
>>>
>>> this patch address some warnings seen during build caused by
>>> const/non-const type-casts. I've noticed them by using gcc 3.4.4 for
>>> bootstrap a cross-compiler.
>>>
>>> ChangeLog
>>>
>>> 2010-06-09 ?Kai Tietz
>>>
>>> ? ? ? ?* gimple.h (gimple_statement_structure): Use const argument.
>>> ? ? ? ?(gimple_ops): Likewise.
>>> ? ? ? ?Do type-cast by union.
>>> ? ? ? ?(gimple_op): Remove use of CONST_CAST_GIMPLE.
>>> ? ? ? ?(gimple_op_ptr): Likewise.
>>>
>>> Tested for x86_64-pc-linux-gnu, i686-pc-cygwin, and x86_64-pc-mingw32. Ok
>>> for apply?
>>
>> +gimple_ops (const_gimple gs)
>> ?{
>> + ?union {
>> + ? ?tree *t;
>> + ? ?const_gimple gs;
>> + ? ?char *c;
>> + ?} v;
>> ? size_t off;
>>
>> ? /* All the tuples have their operand vector at the very bottom
>> @@ -1642,7 +1647,9 @@ gimple_ops (gimple gs)
>> ? off = gimple_ops_offset_[gimple_statement_structure (gs)];
>> ? gcc_assert (off != 0);
>>
>> - ?return (tree *) ((char *) gs + off);
>> + ?v.gs = gs;
>> + ?v.c += off;
>>
>> ugh.
>>
>> Why not simply use
>>
>> static inline const_tree *
>> gimple_ops (const_gimple gs)
>> {
>> ?...
>> ?return (const_tree *)((const char *) gs + off);
>> }
>>
>> ?
>
> Well return of gimple_ops is returning tree * AFAIR. Therefore here is
> const/non-const change necessary, which makes here exactly the issue
> for 3.4.4, as it get warned.
Well, if gimple_ops returns tree * then it shouldn't get a const_gimple.
Your patch just moves the kludge elsewhere (and adds to it with
a ugly union), and thus is not an improvement for const-correcntess.
Richard.
> Kai
>
>
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