fix libbacktrace build failure on arm-linux

On 07.10.2012 12:01, Matthias Klose wrote:
> On 06.10.2012 22:46, Ian Lance Taylor wrote:
>> On Sat, Oct 6, 2012 at 8:09 AM, Matthias Klose <doko@ubuntu.com> wrote:
>>> current trunk fails to build on arm-linux with:
>>>
>>> In file included from ../../../../src/libbacktrace/backtrace.c:35:0:
>>> ../libgcc/unwind.h: In function '_Unwind_decode_typeinfo_ptr':
>>> ../libgcc/unwind.h:42:45: error: unused parameter 'base' [-Werror=unused-parameter]
>>>    _Unwind_decode_typeinfo_ptr (_Unwind_Word base, _Unwind_Word ptr)
>>>                                              ^
>>> ../libgcc/unwind.h: In function '__gnu_unwind_24bit':
>>> ../libgcc/unwind.h:68:41: error: unused parameter 'context'
>>> [-Werror=unused-parameter]
>>>    __gnu_unwind_24bit (_Unwind_Context * context, _uw data, int compact)
>>>                                          ^
>>> ../libgcc/unwind.h:68:54: error: unused parameter 'data' [-Werror=unused-parameter]
>>>    __gnu_unwind_24bit (_Unwind_Context * context, _uw data, int compact)
>>>                                                       ^
>>> ../libgcc/unwind.h:68:64: error: unused parameter 'compact'
>>> [-Werror=unused-parameter]
>>>    __gnu_unwind_24bit (_Unwind_Context * context, _uw data, int compact)
>>>                                                                 ^
>>> cc1: all warnings being treated as errors
>>> make[8]: *** [backtrace.lo] Error 1
>>>
>>> the immediate fix is to mark all arguments as unused, however I don't know if
>>> this function should be used by libbacktrace, if it returns _URC_FAILURE
>>> unconditionally.
>>
>> The function is not used by libbacktrace.  It's an inline function
>> defined in the header file, and the warning is about the inline
>> function definition.  That is, this is a libgcc bug, not a
>> libbacktrace bug, it just happens to show up when compiling
>> libbacktrace for ARM
>>
>>
>>>         * config/arm/unwind-arm.h (__gnu_unwind_24bit): Mark parameters
>>>         as unused.
>>>
>>>
>>> --- libgcc/config/arm/unwind-arm.h      (revision 192162)
>>> +++ libgcc/config/arm/unwind-arm.h      (working copy)
>>> @@ -64,8 +64,11 @@
>>>        return tmp;
>>>      }
>>>
>>> +#define __unused __attribute__((unused))
>>> +
>>>    static inline _Unwind_Reason_Code
>>> -  __gnu_unwind_24bit (_Unwind_Context * context, _uw data, int compact)
>>> +  __gnu_unwind_24bit (_Unwind_Context * context __unused, _uw data __unused,
>>> +                      int compact __unused)
>>>      {
>>>        return _URC_FAILURE;
>>>      }
>>
>> Don't #define __unused.  Just write __attribute__ ((unused)) on the
>> parameters.  Break the lines as needed.
>>
>> This is OK with that change.
> 
> committed the following. the base parameter in _Unwind_decode_typeinfo_ptr
> is unused too.
> 
>   Matthias
> 
> 2012-10-07  Matthias Klose  <doko@ubuntu.com>
> 
>         * config/arm/unwind-arm.h (__gnu_unwind_24bit): Mark parameters
>         as unused.
>         (_Unwind_decode_typeinfo_ptr): Mark base as unused.
> 
> Index: libgcc/config/arm/unwind-arm.h
> ===================================================================
> --- a/src/libgcc/config/arm/unwind-arm.h        (revision 192162)
> +++ b/src/libgcc/config/arm/unwind-arm.h        (working copy)
> @@ -39,7 +39,8 @@
>  #endif
>    /* Decode an R_ARM_TARGET2 relocation.  */
>    static inline _Unwind_Word
> -  _Unwind_decode_typeinfo_ptr (_Unwind_Word base, _Unwind_Word ptr)
> +  _Unwind_decode_typeinfo_ptr (_Unwind_Word base __attribute__ ((unused)),
> +                               _Unwind_Word ptr)
>      {
>        _Unwind_Word tmp;
> 
> @@ -65,7 +66,9 @@
>      }
> 
>    static inline _Unwind_Reason_Code
> -  __gnu_unwind_24bit (_Unwind_Context * context, _uw data, int compact)
> +  __gnu_unwind_24bit (_Unwind_Context * context __attribute__ ((unused)),
> +                      _Unwind_Context *_uw data __attribute__ ((unused)),
> +                      int compact __attribute__ ((unused)))
>      {
>        return _URC_FAILURE;
>      }
> 

and as a follow-up, fix the typo, committed as obvious