[Mesa-dev] [PATCH] fix gcc 8 parenthesis warning

[Ian Romanick]

On 03/23/2018 03:52 AM, Eric Engestrom wrote:
> On Friday, 2018-03-23 11:01:23 +0100, Marc Dietrich wrote:
>> fixes warnings like this:
>> [184/1137] Compiling C++ object 'src/compiler/glsl/glsl at sta/lower_jumps.cpp.o'.
>> In file included from ../src/mesa/main/mtypes.h:48,
>>                  from ../src/compiler/glsl_types.h:149,
>>                  from ../src/compiler/glsl/lower_jumps.cpp:59:
>> ../src/compiler/glsl/lower_jumps.cpp: In member function '{anonymous}::block_record {anonymous}::ir_lower_jumps_visitor::visit_block(exec_list*)':
>> ../src/compiler/glsl/list.h:650:17: warning: unnecessary parentheses in declaration of 'node' [-Wparentheses]
> 
> This is gonna be a *very* annoying warning...
> 
>>     for (__type *(__inst) = (__type *)(__list)->head_sentinel.next; \
> 
> These parentheses are here for a reason: to make sure we can't pass in
> something that would break the code or give it an unexpected behaviour.

This is usually to avoid things with side effects.  Would anything with
a side-effect even compile here?  Or is there some other case that I'm
missing?

> I would be inclined to NAK this patch and request we kill this warning
> at build system level instead.
> Shame when compilers self-sabotage like that :/

This is very annoying because -Wparentheses gives useful warnings when
you don't have () but should. :(

>>                  ^
>> ../src/compiler/glsl/lower_jumps.cpp:510:7: note: in expansion of macro 'foreach_in_list'
>>        foreach_in_list(ir_instruction, node, list) {
>>        ^~~~~~~~~~~~~~~
>>
>> Signed-off-by: Marc Dietrich <marvin24 at gmx.de>
>> ---
>>  src/compiler/glsl/list.h | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/compiler/glsl/list.h b/src/compiler/glsl/list.h
>> index f77fe12991..2bfa273554 100644
>> --- a/src/compiler/glsl/list.h
>> +++ b/src/compiler/glsl/list.h
>> @@ -647,12 +647,12 @@ inline void exec_node::insert_before(exec_list *before)
>>  #endif
>>  
>>  #define foreach_in_list(__type, __inst, __list)      \
>> -   for (__type *(__inst) = (__type *)(__list)->head_sentinel.next; \
>> +   for (__type *__inst = (__type *)(__list)->head_sentinel.next; \
>>          !(__inst)->is_tail_sentinel();               \
>>          (__inst) = (__type *)(__inst)->next)
>>  
>>  #define foreach_in_list_reverse(__type, __inst, __list)   \
>> -   for (__type *(__inst) = (__type *)(__list)->tail_sentinel.prev; \
>> +   for (__type *__inst = (__type *)(__list)->tail_sentinel.prev; \
>>          !(__inst)->is_head_sentinel();                    \
>>          (__inst) = (__type *)(__inst)->prev)
>>  
>> -- 
>> 2.16.2
>>
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